Skip to main content

Full text of "Journal of the Society of Motion Picture and Television Engineers"

See other formats


From the collection of the 



m 

o Prelinger 
* v < JUibrary 



San Francisco, California 
2007 




JOURNAL OF THE SOCIETY OF 

MOTION PICTURE 
AND TELEVISION 

ENGINEERS 

THIS ISSUE IN TWO PARTS 
Part I, December 1951 Journal Part II, Index to Vol. 57 



VOLUME 5 7 
July December 1951 



SOCIETY OF MOTION PICTURE 
AND TELEVISION ENGINEERS 

40 West 40th St., New York 18 



CONTENTS Journal 

Society of Motion Picture and Television Engineers 

Volume 57 : July December 1951 



Listed below are only the papers and major reports from the six issues. See the 
Volume Index for those items which generally appear on the last few pages of each 
issue: Standards, Society announcements (awards, Board meetings, committee 
reports, conventions, engineering activities, membership, nominations, section 
activities), book reviews, current literature, letters to the Editor, new products 
and obituaries. 



Practical Application of High-Speed Photography in Business Ma- 
chines WILLARD L. HICKS and ROBERT L. WRIGHT 1 

Practical Use of Iconoscopes and Image Orthicons as Film Pickup 
Devices K. B. BENSON and A. ETTLINGER 9 

Experimental Utilization of TV Equipment in Navy Training Film 
Production J. S. LEFFEN 15 

Techniques for the Production of Electronic Motion Pictures .... 

E. A. HUNGERFORD, JR. 18 

Practical Operation of a Small Motion Picture Studio 

MORTON H. READ and EUGENE N. BUNTING 23 

Direct-Reading Light Flux Meter 

G. GAGLIARDI and A. T. WILLIAMS 28 

New Processing-Machine Film Spool for Use With Either 35-Mm or 
16-Mm Film F. L. BRAY 33 

Nonphotographic Aspects of Motion Picture Production 

HERBERT MEYER 38 

Improved Kodachrome Sound Quality With Supersonic Bias Tech- 
nique JAMES A. LARSEN 60 

Tape Transport Theory and Speed Control . . J. R. MONTGOMERY 63 

Television Studio Lighting Committee Report . . RICHARD BLOUNT 69 

August 

Data on Random-Noise Requirements for Theater Television .... 

PIERRE MERTZ 89 

Modified Negative Perforation Proposed as a Single Standard for 35- 
Mm Negative and Positive Motion Picture Film . . W. G. HILL 108 

ii Contents: Journal of the SMPTE Vol. 57 



Photoelectronic Method for Evaluating Steadiness of Motion Picture 

Film Images R. W. LAVENDER 124 

Sound Track on Eastman Color Print Film 

C. H. EVANS and J. F. FINKLE 131 
Simultaneous High-Speed Arc Photography and Data Recording 

With a 16-Mm Fastax Camera 

EUGENE L. PERRINE and NELSON W. RODELIUS 140 

Introduction Forum on Motion Picture Theater Acoustics .... 145 

Pulse Methods in the Acoustic Analysis of Rooms J. MOIR 1 47 

Notes on Movie Theater Acoustics in Scandinavia. . . UNO INGARD 156 

Discussion on the Forum on Motion Picture Theater Acoustics ... 159 

September 

Foreword Symposium on Screen Viewing Factors . W. W. LOZIER 185 
The Luminance Discrimination of the Human Eye . . E. M. LOWRY 187 
Influence of Color of Surround on Hue and Saturation . . . . 

DAVID L. MACADAM 197 
Visual Performance on Perceptual Tasks at Low Photopic Brightnesses 

S. D. S. SPRAGG 206 
Surround Brightness: Key Factor in Viewing Projected Pictures . . 

SYLVESTER K. GUTH 214 
Photometric Factors in the Design of Motion Picture Auditoriums 

HENRY L. LOGAN 225 
New Approaches Developed by Relating Film Production Techniques 

to Theater Exhibition 

BENJAMIN SGHLANGER and WILLIAM A. HOFFBERG 231 

Report on Screen Brightness Committee Theater Survey 

W. W. LOZIER 238 
Light Source for Small-Area High-Speed Motion Picture Photography 

RICHARD I. DERBY and ARTHUR B. NEEB 247 
Dynamic Transfer Characteristic of a Television Film Camera Chain . 

W. K. GRIMWOOD and T. G. VEAL 249 

Use of Color Filters in a Television Film Camera Chain 

W. K. GRIMWOOD and T. G. VEAL 259 

Duplication of Color Images With Narrow-Band Filters 

RODGER J. Ross 267 

October 

Electrical and Photographic Compensation in Television Film Re- 
production . . . P. J. HERBST, R. O. DREW and S. W. JOHNSON 289 

Processing 16-Mm Kodachrome Prints 

W. HEDDEN, T. WEAVER and L. THOMPSON 308 

Contents: Journal of the SMPTE Vol. 57 iii 



A System of Double Noise Reduction for Variable- Area Recording for 

Direct-Playback Purposes J. G. STREIFFERT 

The Compliance of Film Loops . G. SCHWESINGER 

Auditory Perspective A Study of the Biological Factors Related to 

Directional Hearing H. G. KOBRAK 

Color Television U.S.A. Standard (4 parts) 

P. C. GOLDMARK, J. W. CHRISTENSEN and J. J. REEVES 
A New Technique for Improving the Sharpness of Television Pictures . 

P. C. GOLDMARK and J. M. HOLLYWOOD 

November 

Dimensions of 16-Mm Film in Exchanges . . . . A. C. ROBERTSON 
Use of Glacial Acetic Acid in Determination of Metol Developer Solu- 
tions . W. R. CROWELL, H. E. GAUSMAN, JR., and H. L. BAUMBACH 

Observer Reaction to Video Crosstalk A. D. FOWLER 

Ultra-Speed Theater Television Optics 

L. T. SACHTLEBEN and G. L. ALLEE 
Independent Frame An Attempt at Rationalization of Motion 

Picture Production G. R. STEVENS 

Progress in Photographic Instrumentation in 1 950 . KENNETH SHAFT AN 
Further Report on Screen Brightness Committee Theater Survey . . 

W. W. LOZIER 

December 

Stereographic Animation NORMAN MCLAREN 

Appendix Generation of Oscillographic Patterns 

CHESTER BEACHELL 

Examination of Some Aspects of High-Quality Television for Motion 

Picture Industry Use . BLAIR FOULDS and E. A. HUNGERFORD, JR. 

The Radial-Tooth, Variable-Pitch Sprocket . . . J. G. STREIFFERT 

Carbon Arcs for Motion Picture Studio Lighting 

W. W. LOZIER and F. A. BOWDITCH 

Magnetic Sound on 16-Mm Edge-Coated Film 

E. E. MASTERSON, F. F. PUTZRATH and H. E. ROYS 

Cine-Interval Recording Camera A. P. NEYHART 

Film Reader for Data Analysis 

WALTER M. CLARK and LEE R. RICHARDSON 
Convention Public Address Committee Report . . . E. W. TEMPLIN 

New Society Emblem Report of the Special Committee 

L. D. GRIGNON 



Contents: Journal of the SMPTE Vol. 57 



Practical Application of High-Speed 
Photography in Business Machines 



By WILLARD L. HICKS and ROBERT L. WRIGHT 



Discussed is the use of a high-speed camera as a tool in the Company's Engi- 
neering Division. Motion of fast moving parts is easily plotted by the use of 
a special timing disc graduated to 0.001 sec. Through the use of negative 
film, film can be processed for study within two hours. 



JL HE DESIGN AND PROVING of the light, 

fast-moving parts in business machine 
mechanisms has been a difficult and 
time-consuming job. Advances in this 
field, while continuous, have been 
obtained only at a high cost in time and 
labor. 

In our study of the action of these 
mechanisms, we had been limited to the 
current instrumentation methods and 
to others which we improvised to record 
time and movement. But we had felt 
for some time that if we could slow 
down or actually stop the normal, rapid 
motion of parts under study, then our 
engineering work would be greatly 
simplified. 

Five years ago our Engineering Group 
had a particularly perplexing problem 
which had been under study for several 
years and to which a number of solutions 
were submitted. The question was 
how could we choose the right one 
without extensive testing. A high-speed 
camera capable of exposing 3000 frames 
a second was procured and put to work 
on this problem. The camera quickly 
proved to the satisfaction of engineering 
the correct solution. 



Presented on May 2, 1951, at the Society's 
Convention in New York, by Willard L. 
Hicks and Robert L. Wright, Standards 
Div., Burroughs Adding Machine Co., 
6071 Second Ave., Detroit 32. 



An entirely new tool had been added 
to our engineering analysis. However, 
it was a problem to sell this method to 
all of our development groups. Today, 
our high-speed camera is very much 
in demand and our camera work has 
developed to the point where we take 
pictures in the morning and have them 
ready for analysis the afternoon of the 
same day. 

The high-speed camera like any other 
analyzing equipment can be used only 
to study or determine trouble if you 
know where to look for it. The mere 
shooting of pictures generally results 
in only exposing film of no value. If a 
machine is missing operations, you will 
have only approximately one second to 
film that operation and may have to 
shoot more than one roll of film to 
pick it up. 

Adding machine operations are rather 
complex. Let us briefly outline one 
of our typical operations so that our 
application of high-speed photography 
can be more readily understood. In the 
hammer section of an accounting ma- 
chine, spring-energized hammers are 
used for printing on rubber platens or 
printer rolls. In this operation we are 
concerned with the initial release of the 
hammer, its acceleration and final 
velocity, the rebound of the hammer and 
type from the printer roll, the deflection 
and vibration of the magazine spring 



July 195 1 Journal of the SMPTE Vol. 57 




that returns the type, the time of reset 
for a repeat stroke of the hammer with 
relation to the complete machine cycle, 
the motion of the hammer on rebound, 
and the degree of certainty of the pickup 
or latching of the hammer in the cycle. 

Now let us consider time in this 
operation. This particular machine is 
operating at 128 printing strokes per 
minute, or less than one-half second per 
stroke. However, the hammer itself 
fires and prints in 0.008 sec and is 
picked up into a latched position in a 
total of 0.130 sec. 

In other mechanisms we have found 
that actual layout displacements are 
increased due to elastic bending while 
in motion. In some cases such over- 
throw movements cause machine lock- 
ups, wrong operations, and fatigue 
failures. 

Time studies, such as those of time 
required for specific mechanical opera- 
tion, accelerations, and velocity are 
made with a timer (Fig. 1) developed 
by Burroughs for our use. This timer 
consists essentially of a 1-in. disc grad- 
uated to 0.001 sec, revolving at 3000 
rpm attached to an 18 in. long shaft 
which can be rotated in two planes. 



Figure 1 

The timer is placed in the field of every 
picture taken with very little sacrifice of 
field. Very precise timing can be made 
while running the film through a time 
study projector, a frame at a time if 
necessary. 

Accelerations, velocities and deflec- 
tions determinations are made by enlarg- 
ing the picture on a screen through a 
time study projector. The picture en- 
largement factor can be obtained by 
photographing a scale in the field of the 
parts to be studied. Displacement can 
then be measured directly. Acceleration 
and velocity are determined by plotting 
time against distance; however, it is 
necessary to center each frame, on the 
screen or paper, on known reference 
points. 

Where we have machine cycles of less 
than one second, it is sometimes neces- 
sary to incorporate microswitches to 
start the camera. The microswitches 
are attached to, and are directly driven 
by, the mechanism to be photographed 
at a required instant in the machine 
cycle. It must be remembered that a 
further allowance of approximately 50 
ft of film may be required to allow the 
camera to reach its maximum speed. 



July 1951 Journal of the SMPTE Vol. 57 



The camera equipment is extensively 
used for the following applications: 

1. To prove plate models of new 
developments before breakdown testing 
and final design. 

2. Improve operation of existing ma- 
chines. 

3. Study the effects of proper and 
improper adjustments. 

4. Establish test fixture comparisons 
of machine movements for correlation 
in testing. 

5. Determining the lag or overthrow 
of cam-driven parts. 

6. Study the flow of metals in shop 
cold working operations. 

7. Study the actions of springs in 
motion. 

A typical lighting setup used at 
Burroughs involves concentrating the 
light beams of four RSP #2 Photospot 
Lamps on the subject, with the lamps 
approximately one foot from the subject. 



A lens opening of//5.6 and maximum 
picture speed of 3000 frames/sec will 
result in good exposure on Kodak 
Super-XX Negative Film. If a greater 
depth of field is required, 750 R Lamps 
may be used so that ample exposure 
can be obtained at the same camera 
speed, while at the same time smaller 
lens openings can be used, thereby in- 
creasing the depth of field. 

Figure 2 is an example of a lighting 
setup for the carriage tabulation picture 
which also shows our camera equipment 
and subject. In this exposure, two 
lamps (RSP #2) placed approximately 
one foot from the subject were used. 
The lens opening was //8. A 50% 
rheostat setting equivalent to approxi- 
mately 1500 frames/sec was used. 

The camera equipment is a standard 
Eastman Kodak Co. Type 3, High- 
Speed Camera with a standard 63-mm, 
//2.7 lens. 



TABULATION SCALE 



I 




Figure 2 
Hicks and Wright: High-Speed Photography 




Figure 3 

Recently, we obtained a new Kodak 
Cine Ektar 25-mm, //1. 9 lens which is 
designed to increase our present 63-mm 
field width by 2 times. This lens will 
greatly expand our present field coverage. 

Eastman Super-XX Negative Film is 
used in taking these pictures, which 
has certain advantages for our use. Its 
ease and time involved in developing is 
a great asset (approximately one hour). 
Enlargements for detailed studies for 
record and report purposes can be made 
directly from the negative film. Then, 
of course, there is a saving on the price 
of the film. To highlight details, parts 
are painted with a flat-white, quick-dry- 
ing, heat-resistant paint. 

Type Hammer Printing 

Figures 3, 4 and 5 represent three 
pictures taken at 2000 frames/sec of a 
critical printing action, the solution 
of which was greatly expedited through 
the use of high-speed photography. 
The cam slot indicated by the arrow 
shown in Fig. 3 represents the portion 
of this action which gave us our trouble. 
In Fig. 3, the spring-driven driver roll 
follows the upper cam surface and 
propels the hammer forward. This 
cam surface is a portion of the hammer 
shown by the arrow. As the roll follows 
this cam surface into the well, it is 
necessary that there be sufficient clear- 
ance between the relatively stationary 



Figure 4 

roller at this instant after firing and the 
cam projection lip indicated by arrow 
(Fig. 3) which is called the cam 
velocity high-point. One thirty-second 
of an inch less clearance on occasion 
will cause the free hammer to rebound 
into the type and print a second time. 
Figure 5 arrow shows this condition if 
you will visualize this section with a 
further build-up of ^ in. on the upper 
cam face. Figure 4 shows the normal 
position of the drive roll on printing. 

The time displacement curves shown 
in Fig. 6 were plotted from this action. 
The hammer displacement was obtained 
by plotting the travel of the hammer 
type contact face on paper shown by 
small arrow in Fig. 5. It is necessary 
to realign the picture between frames 
by centering on established picture reference 
points to compensate for machine move- 
ment while in operation. The actual 
displacement can be obtained by divid- 
ing the projected screen displacement by 
the enlargement factor. The enlarge- 
ment factor can be obtained by dividing 
the enlarged part dimension by the 
actual part size. The time is read 
directly from the timer. 

The curves A "original design" and 
B "corrected design" (Fig. 6) were 
plotted frame by frame. These curves 
indicate we lost little in velocity through 
the reduction of the cam face (Fig. 3) at 
curve point C. Point D graphically 
indicates adequate drive-roll clearance 



July 1951 Journal of the SMPTE Vol. 57 




Figure 5 

between the cam face and the roll. 
Notice the sharp hammer rebound shown 
by E of curve A. Very little hammer 
rebound is occurring between the ham- 
mer and the drive roll as shown in 
curve B. In the picture represented 
by curve B, the height of the rebound 
is approximately 0.045 in. under the 
first displacement. While this is under 
the amount of rebound necessary to 
cause a double print, the tendency to 
double print coupled with machine 
vibration frequency would further 
magnify this rebound. Consequently, 
through the correction of the cam slot 
and further testing, we were able to 
eliminate completely this difficult prob- 
lem. 

Simpler time -displacement plotting 
can be obtained by mounting simple 
reference points on the machine or 
mounting a direct reading scale as shown 
under the carriage tabulation example. 
Occasionally, abnormal actions are un- 
expectedly revealed during film study. 
In such cases, even though reading 
scales were not induced, the information 
for plotting can still be obtained by 
improvisation. Many curves have been 
plotted of this action, involving changes 
in hammer balance, hammer weight and 
spring force. 

Another similar type-hammer printing 
section is shown in Figs. 7, 8 and 9. 
In this example the type magazine is 



1J020 



.765 



.510 



.255 



| TYPE HAMMJER 
TIME-DISPLACEMENT CURVE 




A-ORI6INAL DESIGN 



B-IMPROVED DESIGN 

C-CAM VELOCITY! HIGH POINT 



VELOCITY! H 
CLEARANCE 



D-CAM CLEARANCE 
E- REBOUND CURVE 



.01 



.02 .03 
SECONDS 
Figure 6 



.04 



exposed to show a 0.020 in. diameter 
music wire hair spring. This spring is 
used to restore the type to a normal 
position after printing. The hammer 
and type are highlighted with white 
paint; the spring blackened with carbon. 
The camera speed was 3000 frames/sec. 

The three pictures shown are not 
consecutive frames, but are three of six 
frames embracing a cycle of 0.002 sec. 

In Fig. 7 the second hammer has 
driven its type, while the first hammer 
is about to contact its type. Figure 8 
shows that the first hammer has now 
driven its type ahead of the hammer. 
Note that the type shoe is driving the 
hair spring. Figure 9 also shows that 
the hammer has caught up with the 
type. Note that the hair spring is now 
out of contact with the type shoe. 

The timer reading of 0.006 (Fig. 7), 
from 0.008 as shown in Fig. 9, represents 
a difference of 0.002 sec which is the 
time required for this printing action. 
These pictures were primarily used to 
study the whip action of type hair 
springs, which was so fast that our camera 
speed of 3000 frames/sec was not 
quite fast enough. 



Hicks and Wright: High-Speed Photography 




Figure 7 



Figure 8 




Figure 9 

Multiple-Tooth Engagement 
Drive Clutch 

In this particular application, the 
clutch is required to engage once for 
each complete machine operation. This 
clutch is turning at approximately 130 
rpm. We had experienced some trouble 
with a loss of machine operations, 
caused by the clutch not being com- 
pletely engaged at the beginning of the 
machine stroke. At 180 degrees of 
rotation of the clutch, the machine load 
reverses while the clutch is still rotating 
in the same direction. This machine 
reversal point removes the tooth engag- 
ing pressure, which occasionally dis- 
engaged the clutches. 

A high-speed picture taken at 1500 
frames/sec through an exposed housing 
assembly indicated that this trouble was 



Figure 10 

resulting from a point-to-point tooth 
engagement as shown in Fig. 10. 

Figure 11 indicates a desired tooth 
engagement position under the original 
design. It will be noticed that the left 
side tooth faces are cut at an angle to 
induce positive engagement; but still, 
occasionally improper point-to-point 
tooth engagement resulted (Fig. 10). 

Figure 12 shows a helper pawl in 
position. This pawl prevents point-to- 
point tooth engagement by bearing 
against the entire face of the meshing 
sector. On rotation of this meshing 
sector, the pawl is displaced to allow 
complete engagement of the clutch 
tooth. In this instance high-speed 
photography helped us to eliminate this 
problem and to devise a positive method 
for insuring proper engagement. 



July 1951 Journal of the SMPTE Vol. 57 




Figure 11 



PAWI 



' 



MMMP ^BP 



Figure 12 




Figure 13 



Figure 14 



Carriage Tabulation (see Fig. 2) 

Briefly this mechanism establishes a 
desired stopping position for indexing 
columns of figures on printed paper. 
In this machine-driven operation, we are 
concerned with various carriage weights, 
carriage velocity, friction clutches and 
friction breaks to reduce the carriage 
speed, all of which are timed together in 
the machine cycle and brought to a stop 
position through the action of a spring 
operated bumper mechanism. 

Figures 13 and 14 represent our 
method of plotting a displacement-time 
curve as shown in Fig. 15. Pictures 
were taken at 1800 frames/sec. A steel 
scale is attached to the carriage with a 
fixed reference point. An examination 
of these Figs. 1 3 and 1 4 indicates a time 



I'/Z" CARRIAGE STOP 


/~^ 




"-._ 










t 


/ 




CARR 


IAGE 








/ 




DISP 


LACEMENT-1 
CURVES 


IME 






i \ 




A- BEFORE] REOESGN 
B-jikFTER REDESIGN 




A 


a->^ 


** 


5/8" 


CARRI, 


\GE ST 


OP 




/// 














2 

















.050 .100 .150 .ZOO .250 .300 .350 400 

TIME IN SECONDS 

Figure 15 

change of from 0.0023 sec to 0.0073 
sec for ^ in. of displacement. This 
represents .005 of a second for the time 
required to travel -^ of an inch. In this 
manner the curves shown in Fig. 15 
were plotted. These curves were plotted 



Hicks and Wright: High-Speed Photography 



for -| in. and 1^ in. carriage tabulation 
stops. 

The carriage displacement-time curves 
represent two conditions, Curve A 
"before redesign" and Curve B "after 
redesign." The changes basically 
affected the clutch and brake. The 
carriage weight and tabulation stops 
were picked to represent the most 
critical conditions which were deter- 
mined from previous picture variations. 
The carriage is traveling to the left, 
at the 1^-in. carriage stop position, the 
curve represented by curve A clearly 
shows that more energy is required to 
stop the old design than the new design 
established by curve B. The curve A 
also shows a definite rebound and over- 
throw in the spring bumper on the right 
side, demonstrating that this bumper 
absorbed more energy. The overthrow 
in the left side spring bumper is very 
nearly equal. In the case of the f-in. 
carriage tabulation stop, a greater 
amount of bumper energy absorption is 
required in the old design versus the new 
design. The overthrow in the left side 
bumper is greater and overthrow also 
occurs in the right side bumper. It is 
interesting to note that the curves shift 
to the right in the changed design, 
indicating that a longer total time is 
required to reach the first bumper stop. 
Other changes have been made to further 
improve this example. 

Timer Calibration Method (see Fig. 1) 

The timer consists of an a-c motor 
running at 3570 rpm and a one-inch 
timing disc with 0.001 -sec graduations 
up to 0.020 sec per revolution of the 
disc. A reduction gear train was used 
through a long arm to drive the timing 
disc at 3000 rpm. 

In order to determine the accuracy of 
the above-mentioned equipment, the 
following procedure was followed: 

1. A Strobotac (General Radio Co.) 
was calibrated for 3000 rpm against a 
2-pole synchronous motor at a line 
frequency of 60 0.02 cycles. 



2. The speed of the timing disc was 
then checked against the calibrated 
Strobotac at a line frequency of 60 0.02 
cycles and the speed was found to be 
2992 rpm. This represents an error of 
0.267% below 3000 rpm. 

3. Because our line frequency has 
been known to vary from 59.5 to 60.5 
cycles, these frequencies were then 
used to obtain the maximum and 
minimum timing disc speeds, again 
using the calibrated Strobotac for our 
speed determination. The values ob- 
tained were 2982 rpm at 59.5 cycles and 
3007 rpm at 60.5 cycles. These speeds 
represent an error of 0.6% and 0.233% 
below and above 3000 rpm. 

4. The timing discs were calibrated 
using the following formula: 



60 sec/min 
3000 rpm 



X 1/20 rev./grad. = 0.001 sec. 



The time interval between graduations 
at 2982 rpm is 

f.r\ 

- X 1/20 = 0.001006 sec 



and at 3007 rpm is 

_ X 1/20 = 0.0009977 sec. 



Therefore our accuracy is 0.001 sec + . 6% 

-.23% 

Direct line circuit overloads do not 
affect the timer motor. This was 
checked by a Strobotac. 

This camera is not nearly as com- 
plicated as one would think, and a 
basic operating knowledge of the camera 
can be readily acquired by anyone 
qualified for design and production 
research work. 

It is surprising, even in pictures, how 
much additional information can be 
gained by subsequent viewing of the 
same picture. 

In conclusion, we have found that this 
application of high-speed photography 
enables us through actual pictures to 
analyze quickly mechanical problems 
and arrive at proper solutions. 



8 



July 1951 Journal of the SMPTE Vol. 57 



Practical Use of Iconoscopes and Image 
Orthicons as Film Pickup Devices 

Bv K. B. BENSON and A. ETTLINGER 



At the present time, both iconoscopes and image orthicons are employed in 
monochrome television broadcasting for transmission of motion picture film. 
The theoretical considerations of such operation have been covered quite 
thoroughly in the literature, while the many practical problems have received 
very little attention. A discussion of the correlation between the basic theo- 
retical problems of television motion picture film pickup and their practical 
solutions as presently employed in television broadcasting is given. 



I. ROM A PICTURE and sound reproduc- 
tion standpoint, television film trans- 
mission should equal in quality live pro- 
gramming, just as in aural broadcasting 
recorded playbacks can be indistinguish- 
able from direct pickups. Actually the de- 
velopment of the image orthicon camera 
for direct pickup has progressed so fast 
that the majority of the programs re- 
corded on film do not equal in quality the 
best live pickups. This situation is 
further aggravated, particularly in the 
case of the new television stations, by the 
fact that more emphasis is often placed 
upon studio or live pickups, even though 
a major portion of a station's more im- 
portant program material may be repro- 
duced from film. 

As for the problem of raising the stand- 
ards of television film reproduction, 
there are two roads to follow: one, the 
improvement of presently used equip- 



Presented on May 1, 1951, at the Society's 
Convention in New York, by K. B. Benson 
and A. Ettlinger, Columbia Broadcasting 
System, Inc., 485 Madison Ave., New York 
22, N. Y. 



ment and operating techniques; and 
two, the introduction of new types of 
equipment and methods of film trans- 
mission and pickup. We shall first dis- 
cuss a few of the problems associated 
with the operation of the iconoscope, the 
tube currently used for film pickup at the 
majority of this country's television sta- 
tions, and then we shall describe the 
problems encountered with one of the 
more obvious approaches to new methods 
of film pickup, the use of the image orthi- 
con. 

The iconoscope operating problems 
may be broken down into three cate- 
gories: (1) the proper operating condi- 
tions of the pickup tube; (2) the treat- 
ment of the associated video circuits; and 
(3) the operating techniques for maxi- 
mum picture quality. 

Figure 1 shows the transfer character- 
istic of the 1850A iconoscope for both 
continuous illumination and for pulsed 
illumination such as is used for motion 
picture film pickup. The figures of 
illumination for this latter curve have 
been corrected by a 5% duty-cycle factor 



July 195 1 Journal of the SMPTE Vol. 57 



I.U 










^^^. 


. - 




PULSED ILLUMINATION ^ 
WCBS-TV CAMERA -A \x^' 


^ 


^ 




t 






1 












fi 


CONSTANT ILLUMINATION 1848 
"CORRECTED FOR ISSOA 




.05 


> 


' 


SMALL AREA 


OF VARIABLE 






/ 


INTENSITY IN CONSTANT BACKGROUND 




/ 




OF APPROX. O.I FT- 

1 


CANDLE 




01 


' 











50 100 



Fig. 1. r ,Transfer character- 
istic of the 1850A icono- 
scope for both continuous 
illumination and for pulsed 
illumination. 



FT-CANDLES- 



to average values so as to correspond to 
values for the steady-state curve. It is 
readily apparent that above a value of 20 
to 30 ft-c, the already low value of 
gamma is further reduced. This may be 
interpreted to mean that the tube will 
produce only a minor variation of signal 
output for a rather wide range of film 
densities. Hence, such operation will 
invariably result in serious white com- 
pression. Therefore, if an iconoscope is 
in good condition and used with films of 
normal densities, it should be unneces- 
sary to employ any excessive illumination 
from the projector. In fact, in practice 
a light level such as is produced by a gap 
lamp machine or a 750- to 1000-w incan- 
descent machine with a reasonably fast 
lens has been found ample. Any higher 
value will usually cause some additional 
white compression at the expense of a 
negligible signal increase. Thus, if it is 
found that abnormally high light levels 
are required to obtain a satisfactory 
signal-to-noise ratio, either the icono- 
scope is producing too low a signal out- 
put to be of any further use or the pre- 
amplifier is inadequate with regard to 
noise factor or overall gain. 

Attempts have been made to correct, 
by electrical circuits of nonlinear ampli- 
tude characteristics, the white compres- 
sion or low gamma of the iconoscope 
tube. However, two serious difficulties 
are encountered. For one, the increased 
gain for highlight signals produces not 



only an increase in the highlight signal 
but an increase in the noise level. This 
increase in noise level in the highlight 
area has been found to be quite objec- 
tionable in the reproduced television 
picture. Secondly, the accentuated 
variation in white levels resulting from 
expansion of the highlight signals con- 
siderably complicates the task of the 
video control technician, and his in- 
ability to cope with such changes fre- 
quently results in unsatisfactory tele- 
vision reproduction of the film picture. 

The correction which is desired of the 
transfer characteristic of the overall film 
exposure, development and playback 
process can be obtained by the use of the 
negative film for the iconoscope pickup, 
rather than a positive print. In this 
process, to produce a positive image 
upon the viewing tube, the video signal 
may be reversed in polarity in the film 
camera video amplifier circuits. Both 
calculations and measurements show 
that the resultant transfer characteristic 
not only provides amplitude expansion 
of the picture highlight signals, which 
corrects for the compression of the icono- 
scope and recording process, but, in 
addition, provides a little useful shadow 
expansion. Further, since spurious sig- 
nal effects such as edge flare appear 
black rather than white, they are not 
apparent to the viewer. 

The practicability of such a method of 
transfer characteristic correction has 



10 



July 1951 Journal of the SMPTE Vol. 57 



Fig. 2. Iconoscope transfer 
characteristic for two dif- 
ferent levels of background 
illumination. 



1.0 
.5 

.1 
05 

.01 










^^ 





8 FT-CANOLE 
BACKGROUND 
ILLUM1NATIOI 


S 

> 


^ 


** 






^ 


X 


UNDER 2 FT-CANDLES 
BACKGROUND ILLUMINATION 




_/ 




SMALL AREA 
NTENSITY IN 


OF V 
CONS 


TRIABLE 
TANT BACKGR 


DUND 


1 


5 5 10 50 10 



FT-CANDLES- 



been verified by the success of its ex- 
tensive use at CBS for the release in New 
York of television recordings of feature 
Hollywood programs. Using 35-rnm 
negatives with an iconoscope for pickup, 
CBS has obtained picture quality which 
compares quite favorably with that of 
live studio transmissions. 

Figure 2 again shows an iconoscope 
transfer characteristic, but in this case for 
two different levels of illumination. It 
can be seen that the signal output drops 
with increased average light level, assum- 
ing the maximum and minimum film 
densities have remained the same. Thus, 
in order to maintain as high a signal level 
as possible, and an accompanying high 
signal-to-noise ratio, the spurious light 
level upon the mosaic should be main- 
tained at a minimum and as large a 
mosaic area scanned as is possible. Con- 
sequently, the edge light should be a 
narrow band sharply focused upon the 
extreme edges of the mosaic; the back 
light and iconoscope should be masked 
whenever necessary to direct the light to 
the glass envelope and not upon the 
mosaic; and from the film-production 
angle, exceptionally high key techniques 
should be avoided. Since chromatic 
aberrations exist in the iconoscope glass, 
color filters limiting the back- and edge- 
light emission to a spectrum correspond- 
ing to the peak sensitivity of the pickup 
tube will further reduce the spurious 
light reaching the mosaic. In addition, 



similar optical filters applied to the pro- 
jector light beam will improve the fine 
detail contrast of the reproduced picture. 
In fact, in many cases such techniques 
will produce as much as 50 lines improve- 
ment in detail. 

Figure 3 shows the spectral response of 
the iconoscope and of a filter suitable for 
the above use. It is apparent that while 
the 1850A's response peaks at about 460 
m/z, there is still a fair degree of sensi- 
tivity in the red and infrared regions. 
Such radiation from the film projector 
can be removed quite thoroughly by a 
simple glass filter. 

Aside from the iconoscope itself, of 
prime importance in obtaining the best 
possible reproduction of film is the noise 
factor of the low-level amplifier stages 




Too 



400 500 

MILLIMICRONS- 



Fig. 3. Spectral response of the icono- 
scope and transmission of a filter suitable 
for improvement of detail contrast of re- 
produced pictures. 



Benson and Ettlinger: Film Pickup 



11 



following the iconoscope signal plate. 
Unfortunately, in practice the major por- 
tion of the noise, both of the fine-grain 
shot type and of the low-frequency type, 
from vibration and hum occurs in the 
vacuum-tube video amplifiers, specifi- 
cally those operating at the lowest signal 
levels. Such low levels occur at the first 
stage, and the stage following the con- 
ventional high-frequency compensation 
network. The transfer characteristics 
shown in Fig. 1 indicate that a signal 
output in the order of 1 to 40 mv may be 
obtained under normal operation. A 
similar level will exist after compensa- 
tion. A triode preamplifier, such as a 
6J6, 6J4, 6AK5 or 5654, operating at 
high transconductance and low plate 
current will give good results. The 
iconoscope signal-plate output lead 
should be small bare wire in order to re- 
duce stray capacities to a minimum. 
Shock mounting should be applied to the 
amplifier tube to reduce microphonics. 
As to the compensated stage, here again 
shock mounting should be employed. 
Since input capacities are not too im- 
portant in this stage, the 6BG6 with its 
high transconductance and good stability 
has been found to give excellent results. 
One other likely candidate, the 6AH6, 
has proven to be unsuitable because of 
excessive heater-to-cathode leakage. 
Shielded filament leads for all low-level 
stages will greatly assist in the elimina- 
tion of any stray low-frequency interfer- 
ence. All tubes, except the two above- 
mentioned low-level stages, should be 
operated so as to be capable of consider- 
able voltage swing without compression. 
Frequently, certain operating conditions 
may cause spurious signals to exceed the 
picture information and, if good con- 
servative design has not been employed, 
such operating conditions cause over- 
loading of the video amplifier and re- 
sultant compression of portions of the 
video signal. Needless to say, with such 
low levels of signal all shielding and 
grounding should be very thorough and 
complete. 



From the operational standpoint, there 
are three adjustments which may mean 
the difference between excellent film 
reproduction or just mediocre results. 
These are: (1) iconoscope beam, (2) 
edge light, and (3) back light. All three 
are interlocking in adjustment and if 
properly set up will be satisfactory for a 
wide range of films and will greatly re- 
duce the necessity of continual readjust- 
ment of other controls during a pickup. 
The beam should be set to a point where 
a further increase will produce only a 
minor improvement in signal-to-noise 
ratio. The absolute value of this setting 
will depend directly upon the excellence 
of the video amplifier. An excessive 
beam will cause an objectionable graini- 
ness in the picture plus serious variations 
in shading and edge flare. Once the 
beam is set it will be satisfactory for 
almost all operation. Above all, it 
should not be used as a gain control; all 
video level adjustments should be made 
with the video gain control. With a 
proper beam adjustment, the edge light 
may be set to a level which eliminates all 
flare with a dark scene projected upon 
the mosaic. Best results over a wide 
range in film quality will occur when the 
maximum possible area of the mosaic is 
scanned and a narrow, intense band of 
edge light is employed. To complement 
this adjustment, a setting of the back 
light will be found which will cause a 
reduction of the application pulse. Any 
additional back light will cause excessive 
application pulse and poor field storage 
upon the mosaic. 

Investigation of the Image Or t hi con 

Up to the present time, the use of the 
image orthicon, rather than the icono- 
scope, for film transmission has been in- 
vestigated by relatively few television 
broadcasters. The reasons for this 
limited use have been twofold: first, 
taking into consideration the initial cost 
and the average useful life of the two 
tubes, the hourly cost of image orthicons 
is found to run about three times that of 



12 



July 1951 Journal of the SMPTE Vol. 57 



iconoscopes; and second, to realize 
maximum picture quality, rather ex- 
tensive mechanical modifications are 
necessary on presently available tele- 
vision projection equipment to adapt it 
to image orthicon use. However, the 
increased life of the newer image orthi- 
cons has reduced the operating expense 
somewhat and this factor, plus difficulties 
of procuring good iconoscopes, has made 
the use of the image orthicon for film 
pickup considerably more inviting. 

The major installation problems en- 
countered with an image-orthicon cam- 
era chain are those concerned with the 
modification of the television projector, 
since most of these units are designed for 
the relatively high intensity and large- 
image operation required by the icono- 
scope. The basic requirements for 
image-orthicon application are: (1) an 
image of readily adjustable size from 
approximately 1.2 to 1.6 in. in width; 
(2) a throw of about 14 in.; and (3) an 
illumination level of from 1000 to 5000 
times lower than that normally used for 
the iconoscope. Methods of satisfying 
these requirements are discussed in 
greater detail below. 

The reduced image size may be ob- 
tained by extending the mount of the 
usual 3- or 4-in. projection lens about 2 
in. and focusing the image directly upon 
the image-orthicon photocathode. Such 
an extension of the lens mount must be of 
exceedingly rugged construction; other- 
wise any vibration of the projector will 
result in a loss in accuracy of registration 
of the small image upon the tube. In 
fact, experience has indicated that the 
problem of instability of any longer ex- 
tensions prohibits the use of a lens of 
greater focal length than 4 in. This 
limitation of throw rules out the use of 
the usual method of diplexing two pro- 
jectors through mirrors into one camera. 
If more than one projector is to be used 
with one camera, a turret camera mount 
has proven to be a very practical solu- 
tion. 

The optical focusing arrangement in 



the standard image-orthicon camera pro- 
vides a useful method for adjustment of 
picture size upon the photocathode. 
The arrangement should be such that the 
corners of the projected image slightly 
overlap the periphery of the photo- 
cathode when the image-orthicon tube 
is at the end of the focusing range. As 
the tube is moved forward and the lens 
refocused, the projected image will be- 
come progressively smaller until the 
entire image is within the photocathode 
area. Thus, the image size can be easily 
readjusted to match any reduction of 
scanning raster size necessary as the 
image orthicon ages. The change in 
the position of the projection lens often 
causes an uneven light distribution over 
the resultant image which may be cor- 
rected by removal of one of the condenser 
lens elements. Since this modification 
increases the focal length of the con- 
denser system, it may be necessary to in- 
sert a diffusing glass in place of the 
eliminated lens in order to remove an 
image of the projection lamp filament. 

Several approaches to the problem of 
reduction of light intensity are possible. 
Some light will be lost in the basic modi- 
fication of the condenser lens. In addi- 
tion, since the projection lens will not be 
used at its designed magnification, some 
loss in corner resolution will occur. This 
loss may be corrected, and at the same 
time a light reduction obtained, by 
stopping the lens down about//8 or//ll 
(an opening of about f in.). These two 
expedients provide a reduction factor in 
illumination of 100 or so. In the case 
of the incandescent projector, a further 
reduction in the order of 1 to 20 can be 
very easily provided by the substitution 
of a 50-w or smaller projection lamp. If 
the efficiency of the condenser lens sys- 
tem has not been greatly impaired, a 6-v, 
3-amp, prefocused unit is an even more 
convenient means of reducing the light 
intensity. 

Because of the limited contrast accept- 
ance of the image orthicon, compared to 
the contrast range available from motion 



Benson and Ettlinger: Film Pickup 



13 



picture film, it is essential that a means 
be provided for readily available opera- 
tional control of the projector light level. 
If a small incandescent lamp is employed, 
a simple control consists of a series rheo- 
stat in the lamp circuit. Gap-lamp, 
pulsed light projectors, however, present 
a more difficult problem in light control 
as well as in light reduction. One suc- 
cessful answer consists of a combination 
of a neutral density filter to provide a 
fixed value of light reduction, and two 
Polaroid filters for a variable element. 
The degree of reduction obtained from 
the Polaroids may be varied by rotation 
of one filter in its own plane through sel- 
syn control from the operating position. 
Concerning the image-orthicon cam- 
era, the only absolutely essential modifi- 
cation is the provision for reversal of the 
direction of vertical scan and, if an opti- 
cal diplexing system is contemplated, 
reversal of the horizontal scan. An 
additional and very desirable modifica- 
tion is the removal of the scanning con- 
trols (size and centering) to the camera- 
control position, so as to provide the 
operator with a means of conveniently 
compensating for differences in film 
framing and camera scanning drift. In 
the event that transmission of negative 
film may be required, a switch and cir- 
cuit for reversal of video-signal polarity 
is also required. The quality of the 
transmission of negative film through an 
image orthicon film chain is usually 
poor, however, and consequently such 
operation should be used only in an 
emergency. 



From an operation standpoint, it may 
first appear that the image orthicon 
would require fewer operating adjust- 
ments than the iconoscope because of its 
freedom from shading difficulties; how- 
ever, since electron redistribution effects 
cause the transfer characteristic of the 
image to vary over a wide range as 
average light level and distribution of 
scene brightness change, it, too, requires 
a frequent readjustment of controls. 
Although this factor is not very trouble- 
some with carefully processed film having 
a narrow density range, with the average 
film it may be almost impossible to avoid 
drastic shifts in signal level or sudden 
complete saturation at either end of the 
transfer characteristic. If such changes 
can be controlled, it will be found that 
the image orthicon will produce an 
apparent higher definition than the 
iconoscope. This is because this elec- 
tron redistribution, in effect, creates an 
expanded transfer characteristic in areas 
of fine detail. 

The constant low gamma of the icono- 
scope results in a signal level reasonably 
independent of variations in average film 
densities, while the image orthicon is 
quite critical as to such variations. Thus, 
the image orthicon does not have as uni- 
versal an application to film pickup as 
does the iconoscope, but for films having 
a low density range (in the order of 1 .0 to 
1.5) the image orthicon is capable of 
producing a picture of considerably im- 
proved definition and gray scale over 
that from an iconoscope, and at an 
operating cost not greatly in excess of the 
latter. 



14 



July 1951 Journal of the SMPTE Vol.57 



Experimental Utilization of TV Equipment 
in Navy Training Film Production 



By J. S. LEFFEN 



An acceptable training film can be rapidly produced by utilizing television 
cameras and a video recorder to combine shooting and editing. High equip- 
ment costs and relative immobility of equipment limit application to large- 
scale producers except in cases where speed of production is of paramount 
importance. 



JL HE NAVY has long felt the need for 
a rapid method of producing training 
films for immediate utilization in times 
of emergency. Conventional techniques 
have produced a high-quality product in 
a reasonable time and have been entirely 
adequate for peacetime operation. In 
times of emergency, past experience has 
shown that new equipment is frequently 
produced and in use in the fleet before 
the training film on its operation arrives 
on the scene. 

In an effort to speed up production, 
several experiments, including simul- 
taneous multicamera coverage, have 
been attempted with varying degrees 



Presented on April 30, 1951, at the Society's 
Convention at New York, by Lt. Comdr. 
J. S. Leffen, USN, U.S. Naval Photo- 
graphic Center, Naval Air Station, Ana- 
costia, D.C. The opinions and assertions 
contained herein are the private ones of 
the writer and are not to be construed 
as official or reflecting the views of the 
Navy Department or the naval service 
at large. 



of success. The Naval Photographic 
Center's successful experimentation with 
kinescope recording aroused an interest 
in the possibility of utilizing television 
equipment in motion picture production. 
It was believed that an acceptable 
continuous "edited" negative of a ten- 
minute training film sequence, complete 
with titles and effects, could be pro- 
duced by use of two or three camera 
chains, a camera switching and effects 
unit and a kinescope recording unit. 
By the addition of standard double 
system sound, title music, narration, 
dialogue and sound effects could be 
added. The actual production would 
then consist of rehearsal, shooting and 
processing, completely eliminating the 
editorial phase. While it was realized 
that use of present television scanning 
standards would inevitably lead to some 
sacrifice of pictorial quality, it was 
believed that in view of the probable 
saving of time, this loss would be ac- 
ceptable for some types of subject 
matter. 



July 195 1 Journal of the SMPTE Vol. 57 



15 



A survey of available commercial 
equipment disclosed that the products 
of several manufacturers would probably 
fulfill our requirements. One manufac- 
turer (General Precision Laboratory of 
Pleasantville, N.Y.) offered to make a 
two-camera chain, a camera switching 
unit and a kinescope recording unit 
available for experimentation. Note- 
worthy features of this equipment are: 
small size of the camera units, use of 
picture tube blanking rather than a 
mechanical shutter in the video recorder 
and addition of a "gamma correction 
amplifier" in the video chain of the 
recorder unit. 

Since a project was on the books 
which seemed a natural for the proposed 
type of production technique, the offer 
was accepted and script writing com- 
menced. In view of the probable 
difficulties to be encountered with wholly 
unfamiliar equipment, it was decided 
to keep the script as simple as possible. 
Subsequent events proved this a wise 
decision. 

The equipment, upon arrival, was 
found to have been severely handled in 
shipment. Several days were spent in 
making temporary repairs and adjust- 
ments. This rough handling may have 
also been partially responsible for the 
continuous minor difficulties and failures 
which plagued the remainder of the 
experiment. 

The manufacturer's experience in 
video recording had been primarily in 
production of a positive by photo- 
graphing a negative image on the 
kinescope. It was originally planned 
to make extensive sensitometric tests 
with varying camera settings, video 
gamma, exposure and gamma of de- 
velopment to get the best possible 
negative. The initial loss of time due 
to equipment damage made it necessary 
to seriously curtail these tests and they 
were abandoned completely as soon as a 
usable negative was produced. The 
emulsion stock used was Eastman Kodak 
Company $7373, a sound recording 



stock. This was in line with the film 
and equipment manufacturers' recom- 
mendations for kine recording for sub- 
sequent retelecast. It is possible that 
another emulsion might have been more 
suitable for the ultimate production of 
projection prints. 

The video equipment was set up with 
the cameras on the sound stage, the 
camera control, switching and monitors 
in the stage projector booth which over- 
looks the stage and the video recorder 
in a room remote from the stage. The 
camera control operators and director, 
who operated the camera switching unit, 
were stationed in the stage projector 
booth. Two-way headset communica- 
tions were, available between the director 
and the assistant director and camera- 
men of the stage. 

The sound mixer was stationed in a 
monitor room on the second deck 
overlooking the stage. From this posi- 
tion, he controlled the re-recorder used 
for title music and rode gain on the 
narration. An "on the air" picture 
monitor was provided at this station. 
In this temporary installation, it was 
necessary to leave the stage and pro- 
jector booth doors open to provide 
passageway for cables. This resulted 
in a substantial increase in ambient 
noise level. To combat this, the nar- 
rator was provided with a microphone 
on a chest plate. This resulted in an 
improved signal-to-noise ratio and 
greater freedom of action. It was 
hoped that the remainder of the ambient 
noise would simulate that of the scene 
depicted. 

Completion of repairs, sensitometric 
tests and setup required so much time 
that it was necessary to commence 
rehearsals simultaneously with indoctri- 
nation in equipment operation. 

So little time remained to use the 
equipment, that it was decided to 
dismiss technical defects such as poor 
sweep linearity, improper view-finder 
alignment and less than optimum 
lighting and print quality as factors 



July 1951 Journal of tfi<j SMPTE Vol, 57 



which could be corrected if time were 
available, and to proceed with re- 
hearsals and shooting. 

With the commencement of rehearsals, 
additional difficulties were encountered. 
It was discovered that the detents on 
the camera-lens turrets were not strong 
enough to position positively the ten-inch 
lenses. Since these lenses could not 
be used, more camera movements were 
required than had been originally 
scheduled. 

In all, a total of fourteen hours of 
rehearsal and shooting were required. 
While this may seem inordinately long, 
it should be remembered that neither the 
director nor the cameraman had ever 
used television equipment before. The 
director was performing the dual job 
of director and technical director. 
With the exception of the narrator, no 
professional acting talent was employed. 

The original objective of producing a 
continuous negative in one take was not 
quite achieved. As time ran out, one 
almost perfect take was made and only 
enough time remained to make two 
short pickup shots. 

Although this experiment was too 
limited in scope to justify definite con- 
clusions, the following general compari- 
sons with standard motion picture 
equipment and techniques appear to be 
ustified: 

1. The equipment is not fully port- 
able. This remark applies particularly 
to the video recorder unit. 

2. The equipment is not completely 
reliable. While engineered and manu- 
factured to high standards, failures are 
much more common than in the more 
familiar motion picture sound equip- 
ment. Constant maintenance is re- 
quired. 



3. A larger production crew is re- 
quired. The minimum increase con- 
sists of one camera control unit operator 
for camera, a technical director and an 
operator for the video recorder. 

4. Substantial saving in time and 
complete elimination of editorial and re- 
recording cost is possible. 

5. Pictorial quality, while not up to 
motion picture standards, is acceptable 
for most types of subject matter en- 
countered in training film production. 
The picture looks better than a purely 
mathematical analysis of resolution 
would indicate. 

6. Sound quality, due to the elimi- 
nation of several re-recording genera- 
tions, is better than average for 16- mm 
prints. 

In conclusion, the high initial cost of 
television equipment requires a large 
volume of production before reduction of 
editorial costs make this type of opera- 
tion economically feasible. The large 
amount of time saved might make this 
technique desirable for some producers 
in spite of the economic penalty. 

From the Navy's point of view, the 
production workload does not appear 
to warrant purchase of such equipment 
at this time. In time of full mobiliza- 
tion, when the workload greatly in- 
creases and production time must be 
greatly shortened, it is probable that 
serious consideration will be given to 
employing this technique. 

Acknowledgment is hereby made to 
the personnel of General Precision 
Laboratory, whose enthusiastic coopera- 
tion made this experiment possible. 
The film made in the course of the 
experiment is now in use and is ade- 
quately fulfilling its purpose. 



J. S. Leffen: TV in Film Production 



17 



Techniques for the Production of 
Electronic Motion Pictures 



By E. A. HUNGERFORD, JR. 



This paper examines the techniques now current and estimates the possi- 
bilities of accomplishing the production of truly electronic motion pictures of 
sufficient technical quality to reproject into the television broadcast channels. 



OEVERAL high-speed techniques for 
motion picture production have made 
their appearance in the last few years. 
The goal of these techniques is to produce 
motion pictures at a cost the television 
industry can afford to pay. All of these 
techniques are logical progressions to- 
ward the ultimate method of producing 
movies using high-resolution television 
cameras which feed to high-quality video 
recorders for picture and the usual film 
recorders for sound. 

Television broadcasting has grown 
much more rapidly than was ever antici- 
pated. With this growth has come a 
demand for visual programming which 
severely taxes the facilities and talent of 
the entertainment world. 

In the beginning, television borrowed 
from all existing allied fields. From the 
theater came talent who could give a 
sustained performance since television is 
a real time medium. From radio came 



Presented on May 3, 1951, at the Society's 
Convention at New York, by E. A. 
Hungerford, Jr., General Precision Labora- 
tory, Inc., Pleasantville, N.Y. 



the know-how in electronics and the 
production techniques for handling spe- 
cial events and sports. From radio, too, 
came money by the millions of dollars. 
Even though radio knew that nurturing 
television would put its balance sheet in 
jeopardy for the years until television 
became profitable, radio plowed ahead 
with full confidence that the day of 
profits would eventually come. It is 
now nearly here. One great television 
network has recently reported black-ink 
operations; many individual stations 
have achieved this goal. 

Television borrowed from motion 
pictures, too. A visit to the early tele- 
vision studios was a visit to Hollywood in 
miniature. The lights were identical; 
the camera dollies were the same; so 
were the microphone booms. Every 
applicable production trick was borrowed 
to get television under way. 

Production Time Reduced 

Soon some changes began to occur. 
Fixed lighting was replaced by systems 
which could be controlled during per- 
formances. New types of dollies ap- 



18 



July 1951 Journal of the SMPTE Vol, 57 



peared. New techniques developed. 
Always the goal was the same to speed 
up production of visual material. In the 
last ten years much progress has been 
made in fast techniques for television 
production. For example, complete 
one-hour dramatic programs are pro- 
duced in three to five weeks. Actual 
camera rehearsal time is often only eight 
to twelve hours. Yet the final produc- 
tion is much like a feature motion pic- 
ture. Since most such programs are 
produced live, the actors give sustained 
performances, which further heightens 
the effect. 

Television has now grown up and is 
ready to pay its debt to motion pictures. 

Some of these same high-speed tech- 
niques are adaptable to the moving pic- 
ture industry and will bring the costs of 
production down to a point where tele- 
vision can pay for the costs involved. 

At this point it is appropriate to ask 
the question, "Does Hollywood really 
want to produce films for television?" 
The answer must come back in the 
affirmative for several reasons. First of 
all, the quantity of film required by tele- 
vision so far exceeds the imagination that 
from a quantity viewpoint alone the 
market is attractive. And if production 
can be artistic, too, it will represent a 
real challenge to the ingenuity of Holly- 
wood. But there is another very big 
reason. This has its roots in the theater, 
the outlet for Hollywood products. The 
theater today is undergoing a major 
adjustment. It is faced with direct com- 
petition for the first time: a small but 
lively lighted bottle in millions of tele- 
vision homes essentially moving pic- 
tures, even though on pocket-sized 
screens. Many theaters realize that the 
best way to fight fire is with fire and the 
move to theater television is on. What 
will this mean? 

Already one or two theaters are piping 
a television newsreel to their big screens. 
Television can and does do news better 
than the newsreels can hope to do. 
Soon there will be special events for 



theater television. * Some circuits even 
plan their own studios to generate variety 
shows for their big screen theater tele- 
vision. This will inevitably take away 
playing time from feature pictures. It 
now seems probable that the second fea- 
ture may ultimately be replaced by 
theater television productions. To 
Hollywood this must mean less feature 
picture production for the theater, more 
overhead to spread over fewer pictures. 
This is hardly the way for an industry to 
advance in these competitive times. So 
Hollywood will have to look to a new 
market to make more efficient use of its 
splendid facilities for picture production. 
In seeking this new market no matter 
where it turns, Hollywood will encounter 
television and its voracious appetite for 
visual material. 

To serve this market Hollywood will 
have to devise lower cost production 
methods because the day is still distant 
when television can spend $1,000,000 
and up to run a feature picture. So, 
now motion pictures can borrow back 
from television some of the tricks which 
television has of necessity had to develop 
to cut its own production costs. Already 
the gap is being closed between high- 
and low-cost production. Let us ex- 
amine the progress to date and see 
where it leads. 

The Search for Economy 

About a year ago an experiment was 
begun in Hollywood in connection with 
the Groucho Marx television show. The 
performance was strictly a radio show 
played in a typical radio studio. On the 
stage was a plain backdrop in front of 
which Mr. Marx seated himself on a 
stool. Here he met and interviewed his 
guests. From the center stage angle and 
shooting from the audience was a 35-mm 



*Since the writing of this paper, several 
showings of sporting events have been 
made over exclusive theater television net- 
works. The success of these demonstra- 
tions has proved beyond doubt the prac- 
ticability and appeal of this medium. 



E. A. Hungerford: Electronic Motion Pictures 



19 



motion picture camera. From stage 
left and from stage right were two other 
35-mm cameras all three grinding 
away continuously. At each location 
was another camera loaded with film and 
ready to take over when the active cam- 
eras ran low on film. In this way con- 
tinuity could be maintained indefinitely. 
The cameras at stage left and stage right 
concentrated on close-ups while the cam- 
era at center stage angle provided the 
cover shot. By skillful editing, a motion 
picture was produced which had high 
impact and which constituted a very fine 
television show of high technical quality. 

Here was a motion picture made in 
real time and, though a lot of film was 
probably destined for the cutting room 
floor, this waste was not large in terms of 
the value of the show as a whole. Yet 
the search for greater economy con- 
tinued. 

Next a system was devised where the 
director of the production would turn on 
a selection of motion picture cameras on 
cue to photograph a rehearsed script so 
that only the desired shot was being 
recorded on film. This saved film and 
also simplified editing and reduced the 
time from shooting to a finished print. 

Evolution of Electronic Techniques 

This latter system is much closer to the 
television technique in that some editing 
is attempted in the shooting of the scene. 
Then came the Vidicam system. 

This next step was inevitable the 
transition to the use of electronic view- 
finders on film cameras. This system, 
now in actual use by the Vidicam Pictures 
Corp. of New York, operates as follows: 
To permit the producer to see what he is 
shooting a small television camera is 
mounted alongside the motion picture 
camera. The television camera is me- 
chanically adjusted to see the same scene 
as that being viewed by the motion pic- 
ture camera. The production is handled 
just as a television program would be 
handled. The director selects his shots 
on television monitors and instructs his 



cameramen in proper movement. When 
he selects his television shot he simul- 
taneously starts the associated motion 
picture camera. Suitable bloops are 
applied to the sound track to assist in 
editing. This is really television produc- 
tion monitored by celluloid recording. 
Editing is practically accomplished as 
the production unfolds. Little or no 
film is wasted. Here is efficient produc- 
tion. The sustained performance is en- 
couraged to the greatest extent possible. 
It is now practicable, with such a system, 
to turn out two 15-minute dramatic bits 
completely in a day's time including all 
rehearsals. 

It is but a short step from Vidicam to 
the fully electronic technique. The 
motion picture camera is merely moved 
back into the laboratory next to the 
sound recorder and the picture is re- 
corded in like manner by photographing 
a high-quality television image of suit- 
able brilliance. Here is the way to cap- 
ture all the time saving elements of tele- 
vision production for only television 
equipment is used. Picture recording is 
handled exactly as sound recording has 
been handled for twenty years. Tele- 
vision is paying back its debt to motion 
pictures. In return for the techniques 
borrowed in its earliest beginnings, tele- 
vision returns a smooth high-speed pro- 
duction technique well suited to turning 
out films for television use on a mass 
basis. 

The Need for Higher Quality 

The above technique viewed another 
way is really a kinescope recording and 
as such does not enjoy an enviable repu- 
tation for quality as yet. But the results 
are improving fast and over the past two 
years new equipment has come on the 
market which equals the best that can be 
done with 16 -mm film even when photo- 
graphed directly. And these results can 
be still much better. Present-day tele- 
vision camera equipment is designed to 
feed television transmitters for home 
television. The limitations in the trans- 



20 



July 1951 Journal of the SMPTE Vol. 57 



mitters and in the home receivers are 
dictated by the standards set for home 
broadcasting. It is possible, however, 
to build far better television cameras and 
associated equipment, including video 
recorders, which will produce results 
closely approximating those obtained by 
direct photography on 35-mm film. 

Within a year such equipment will be 
available to the motion picture producer. 
This will enable him to use all the tele- 
vision techniques to produce electronic 
motion pictures whose quality, when 
transmitted over the commercial broad- 
cast channels, will exceed that presently 
available from the best live talent pro- 
ductions. 

Design personnel at this Laboratory 
are about to introduce a higher resolu- 
tion television system. The need for this 
is well recognized in the field of theater 
television. Present broadcast standards 
of four megacycles are insufficient to 
meet the requirements of large-screen 
projection in the theater. The new 
cameras and associated equipment will 
produce pictures which are nearly twice 
as good as present-day broadcast images. 
When such images are recorded on 
equally good video recording equipment, 
the resulting motion picture film will 
approximate the quality of 35-mm 
original photography. 

How then, will this transition to elec- 
tronic motion picture production be 
made? It will probably occur in several 
different ways. The first successes will 
come to those who are already experi- 
menting with high-speed motion picture 
production methods, like Vidicam. They 
will adapt quickly and easily to the new 
technique. They are practically there 
already. By the addition of a video re- 
corder, a continuous rapid processor and 
a projector it is now possible to expand 
the Vidicam system to produce an 
"answer" sound print which the sponsor 
can have immediately for approval and 
review. Such a system for audition 
work and rehearsal "rushes" can be the 
most economical short-cut to fast produc- 



tion. If high-quality television cameras 
are used with Vidicam systems, the day 
will soon come when the electronic re- 
cording will suffice for most purposes 
for telecasting, review and nontheatrical 
distribution. 

The armed services are also a factor in 
this area. Always alert to any method 
for producing training films in less time, 
the Navy Photographic Center recently 
made a test film using television equip- 
ment supplied by this Laboratory. This 
experiment is the subject of the paper by 
Lt. Comdr. J. S. Leffen in this issue of the 
JOURNAL. It is only necessary to state 
here that the experiment was successful: 
a 20-minute training film was produced 
in fourteen hours of camera time. Ex- 
perience would cut that figure appre- 
ciably. 

At the Navy Special Devices Center, 
experimentation with the effectiveness 
of television for education has been going 
on since 1946. To better study the re- 
sults of experimental programs kinescope 
recording facilities were installed at the 
Center. As a part of the competitive 
testing of live classroom instruction versus 
live television training, a test of the 
kinescope recordings was also conducted. 
This latter phase proved that the record- 
ings had nearly the same impact as the 
live television performance. It soon be- 
came apparent that the kinescope re- 
cordings were a very valuable end prod- 
uct in themselves. They were used ex- 
tensively in training. This work led to 
the experiment at the Naval Photo- 
graphic Center, the results of which you 
have seen. 

Hollywood producers in the larger 
companies will probably arrive at this 
electronic motion picture technique by 
another route. When the motion pic- 
ture theaters begin to exploit theater 
television extensively, they will look to 
Hollywood to supply the material to 
transmit to the theater, just as they have 
always looked to Hollywood for screen 
fare. To meet these requirements, the 
major studios will undoubtedly install 



. A. Hungerford: Electronic Motion Pictures 



21 



television equipment and begin to gain 
the necessary experience with the tech- 
nical phases of the television medium so 
that they can bring to bear the full force 
of their artistic achievement. In meet- 
ing this need, there will be many times 
when it will be more efficient and ex- 
peditious to produce these theater tele- 
vision epics during the day rather than 
at the particular time required by the 
theater schedule. So these programs 
will be recorded by high-quality video 
recording apparatus and played into the 
circuit at the appropriate screen time. 
At this point, or before, Hollywood will 
be in the thick of producing electronic 
movies and will have become so skilled in 
these techniques that networks will be 
vying with one another to buy such a 



product. The age of the electronic 
motion picture will have been born. 
The motion picture and the television 
industries will have moved many steps 
closer together. This is, of course, 
essential for the continued growth of 
each. 

As the television medium assumes its 
full national stature and becomes a 
broadcasting industry of greater scope by 
far than radio, it will offer a new and 
tremendous market to the motion pic- 
ture industry for a suitable product, a 
market which can be efficiently and suc- 
cessfully met by the adoption of high- 
speed motion picture techniques and, 
finally, fully electronic motion picture 
production techniques. 



22 



July 195 1 Journal of the SMPTE Vol. 57 



Practical Operation of a Small 
Motion Picture Studio 

By MORTON H. READ and EUGENE N. BUNTING 



The problems and methods of handling television film commercial and 
short productions economically and in a limited space are outlined. 



J. HE TERM "small" as applied to 
motion picture production studios is a 
relative one, and its proper use depends 
entirely on comparison. I have no 
idea how the operation of our business 
compares to the film business in general 
with the exception of specific cases 
which are familiar to everyone in the 
industry. Thus, we are very small 
as compared to Hollywood theatrical 
operations, small when compared to the 
larger and better known of the so-called 
industrial producers, but perhaps the 
term "medium" might be applied to our 
operations when compared to the many 
organizations which operate on a much 
smaller scale than do we. So that the 
reader of this paper may find his own 
estimate of our size, the following list 
may be helpful. 

1. A sound stage of 3000 sq ft, 

2. Camera and lighting facilities in- 
cluding a portable 1 5-kw field generator, 

3. Sound Department, including a 
16-mm film recorder, ^-in. and 17^- 
mm magnetic recorders and phono- 
graphs, 

4. Printing facilities for black-and- 
white and color duplicates. 

5. 16-Mm black-and-white machine 
processing, 

6. Cutting, editing and screening 
facilities, 

7. Animation facilities, and 

Presented on April 30, 1951, at the Society's 
Convention in New York, by Morton H. 
Read, President, Bay State Film Pro- 
ductions, 458 Bridge St., Springfield, Mass. 



8. A production, creative and sales 
staff, totaling 15 persons. 

There is more than one reason why 
small motion picture studios exist. 
The reason can be from the standpoint 
of: (1) economics, (2) efficiency, or 
(3) business conditions peculiar to a 
given geographical area. All of these 
reasons have had an effect upon our 
growth, the last one most of all. 

New England is different from some 
sections of the country when it comes to 
spending money. Our clients want 
quality, but they don't want to pay 
what they call "fabulous prices" for 
motion picture production; and, in 
fact, if New England clients could not 
buy motion pictures within certain 
price ranges, they would not buy at all. 
But in spite of our limitations and 
conditions imposed upon us, we must 
produce motion pictures which compare 
favorably with those produced by al- 
most anyone else in the business. 

The increasing number of television 
productions has made it necessary to add 
speed without sacrificing quality, a 
requirement which we feel has added 
to, rather than subtracted from, effi- 
ciency. And so we have developed 
certain techniques to accomplish what 
must be done, some new versions of old 
methods and some new. 

Perhaps the most important factor 
in the successful operation of a small 
studio is the selection of a staff. This 
selection may make or break the business 
because the cost of overhead is the 



July 1951 Journal of the SMPTE Vol. 57 



23 



a 










Fig. 1. 
Studio 
Arrangement. 



greatest single enemy. Wherever pos- 
sible, it is desirable to select or train 
men who are capable in more than one 
phase of production. 

There is almost no place for single-job 
specialists here. To be sure, there will 
have to be some single-job men such as 
those in the laboratory who are closely 
confined to their work; but our three 
cameramen must also do lighting, 
animation, editing, matching, cutting 
and splicing. Our sound engineer must 
also be the recordist, do musical scoring 
and maintain the equipment. For that 
matter, anyone who elects to spend his 
business life in a small motion picture 
studio, must plan to do many different 
operations. Some might think that 
such a set-up makes for inefficiency and 
chaos, but there is advantage in close 
cooperation and integration, which make 
possible a follow-through well nigh 
impossible in any other type of organi- 
zation. 

Set design in a small studio can be 
something of a problem, especially if it 
is necessary to have several sets ready 
at the same time. When budgets are 
low and space is limited, casts cannot 
be kept on subsistence while sets are 
changed and the studio is rearranged. 



This is especially true when a series of 
television commercials involves (as they 
often do) a kitchen, dining room, living 
room, hallway with front door, etc. If 
the studio can be completely set up in 
advance with all top lighting in place, 
it's possible to do a vast amount of work 
in a minimum of time. 

Studio Arrangement 

Figure 1 illustrates a type of studio 
arrangement which is probably not 
original, but which we have not seen 
elsewhere. It provides four fairly siz- 
able, two-wall sets and four smaller 
two-wall sets. The four corners of the 
studio are used for kitchen, bedroom, 
dining room, living room, etc., while 
the unit in the center will handle a 
small bathroom, a hallway, doorway 
room corner, etc. This center unit is 
rather interesting since it is designed 
to fold flat and can be wheeled out of 
the way on a small dolly. This ar- 
rangement would not work too well for 
production demanding three-wall sets, 
but it works to great advantage in 
television and allows complete use of 
the entire sound stage. In planning a 
shooting schedule, it will be found more 
efficient to complete scenes in the center 



July 1951 Journal of the SMPTE Vol. 57 



section first, then roll that section out 
of the way for work on the corner sets. 

Many small producers have made a 
practice of doing television work on 
location and, in isolated cases, such a 
procedure may work to advantage. In 
our experience, however, it is always 
preferable to work in the studio where 
every phase of production is under 
control. 

Production techniques in small studios 
are, of course, based on standard prac- 
tices worked out by the experts. Almost 
everyone who does not possess facilities 
for manufacture or development, buys 
his entire equipment packaged and 
ready to use. But it would require a 
lot more money than the usual small 
producer has, to own everything he 
will require to accomplish the great 
variety of demands which will be made 
upon him. It is then that his ingenuity 
must be put to work if he is going to 
compete. It is then that gimmicks and 
gadgets make their appearance and 
equipment begins to do and do well, 
jobs that were never intended for it. 
Many Bell & Ho well projectors have 
been modified with synchronous motor 
drive. Old projector amplifiers are 
now doing duty as parts of sound readers 
and many fine old cameras are working 
again in various versions of an optical 
printer. The adaptations are not hay- 
wire. They are doing a good practi- 
cal job. The small studio is what 
it now is because of ingenuity and hard 
work. 

At this point in the Convention 
presentation there was shown a short 
portion of a color print, The Will to Be 
Remembered, produced for the Barre 
Granite Association, Barre, Vt. 

Improvisation 

There was more than one reason why 
the print projected was chosen for the 
meeting. Besides the subject matter, 
it is a typical example of production 
in a small motion picture studio. By 
that, I mean the use of equipment never 



intended to do the work for which it was 
made. A small production unit ad- 
vances slowly in its acquisition of fine 
cine equipment, but it still must turn 
out the work. 

The print was made on a Depue, 
double-head, continuous printer operat- 
ing at 76 ft/min. A resistance light 
control board was used for varying light 
intensity and all fades and dissolves 
were made simply with A&B rolls and 
cutting the current from the printer 
lamp. Obviously, with a double-head 
machine, the sound track was printed 
in contact, but should it seem that the 
whole list of taboos for color printing 
has now been completed, there is one 
still to come. The re-recording of the 
voice track was made from a standard, 
synchronously driven, Bell & Howell 
projector. No change was made in the 
optical system although resistance and 
matching systems were introduced in 
the projector amplifier output. 

This system of re-recording is one we 
have long since abandoned but, though 
unorthodox, it can be made to work 
well. For some time now, we have 
been using a system of magnetic tape 
transfer in re-recording. Perhaps this 
method of tape transfer might be 
interesting to those who are not blessed 
with three-phase interlock and all that 
goes with it. We were using magnetic 
transfer long before there was any 
publicity about it and the method is so 
simple that anyone can use it. Our 
particular set-up involves a standard 
Magnecorder, ^-in. tape recorder and 
a Kinevox 17^-mm magnetic film 
recorder and phonograph. Since manip- 
ulation of the starting switch on the 
Magnecorder will allow the drive mech- 
anism to operate without transporting 
tape, it is possible to start and stop the 
transport at any given time. Our 
system is to measure the final cut work 
print of a film and provide the recordist 
with a copy of the script which has 
each section of the narration marked 
off in linear measurement. By refer- 



Read and Bunting: Small Motion Picture Studio 



25 



ring to a synchronous footage counter 
and starting and stopping the Magne- 
corder as indicated, it is a simple matter 
to transfer wild narration track to the 
synchronous magnetic film in just ten 
minutes per reel. There is no cutting 
of tape or film track, no bloops to worry 
about, no worry about the handling 
of the medium which is to be recorded. 
If the recordist makes an error, he 
simply notes it, finishes the reel and then 
goes back to erase the area where the 
mistake was made so that he can fill 
in that particular narration. 

There is no controversy between the 
theoretical and the practical in the small 
motion picture studio. I feel sure that 
everyone in the business would be per- 
fectly equipped if he had the choice. 
But any business must grow and in 
growing must turn out quality or fall 
by the wayside; and if survival is the 
only reason, a way will be found to make 
quality a reality. The small studio 
has one very great advantage over its 
larger counterparts. That advantage 
is a close-knit, compact organization 
with little or no distance between the 
man who develops an idea and the man 
who executes it. We are blessed with a 
group every one of whom is vitally 
interested in turning out the best possible 
job. Since a great many small studios 
survive and continue to grow, it seems 
safe to assume that our situation is not 
peculiar to us. 

Most small producers rely on practical 
methods of control throughout the whole 
operation. It sounds trite to say that 
such control is merely the judgment of 
what looks and sounds good, but in 
effect that is so. In color work es- 
pecially, the highly specialized machinery 
for color analysis is denied the small 
studio because of cost alone, and some 
other means must be found to bring 
about consistent results. A good deal 
of interest has been expressed in our 
particular color control methods and 
although I feel quite sure that they are 
not greatly different or outstanding, 



they are outlined below. The methods 
may prove interesting simply as a means 
of comparison to those in general use. 
The basic rules are as follows: 

1. Employ as few color correction 
filters in the printer pack as possible. 

2. Careful voltage control of the 
printer exposure lamps. 

3. Standardized test for each stock 
emulsion number. 

4. Standard color patches on each 
print. 

Color Control 

The gauge or color patch consists of 
twelve color patches representing differ- 
ent mixtures of the three basic colors, 
magenta, cyan and yellow. Because 
corrections are to be made visually 
and not by instrument, each patch is a 
full frame in size. In our opinion, it 
is important that these patches are 
not pure basic colors, since if they were, 
small contamination by an odd color 
would not be easily detected. These 
color patches are made up of 50-50 
mixtures of cyan-yellow, yellow-ma- 
genta, magenta-cyan and certain devia- 
tions from the 50-50 mixtures. We 
find that these patches reveal errors 
that may be quite small. [Slide pro- 
jected here.] The patches at the top 
of the slide are the original ones shot in 
the camera; those in the center are a 
set from several hundred which were 
duplicated in the printer and which 
are attached to each print; and those 
at the bottom were cut from a print. 

When a stock test or print returns from 
the laboratory, the color patches are 
visually compared over a constant light 
source with the gauge from which it was 
printed. It would be very unusual to 
find all patches out of balance, rather 
than only those most affected by the 
color which is in the wrong proportion. 
Thus too much yellow in the filter pack 
will not greatly affect those patches 
which are made up of a high percentage 
of yellow nor will too much magenta 
greatly affect the magenta patch. 



26 



July 1951 Journal of the SMPTE Vol.57 



But an excess of magenta, will show 
up in the green patch causing it to turn 
brownish by comparison with the original 
from which it was printed. Similarly, 
an excess of yellow would be detected 
in the violet patch by causing it to 
appear reddish by comparison to the 
original; and an excess of cyan would 
be apparent in the yellow patch by a 
green cast. 

It is surprising how this comparison 
test will show up even minute discrepan- 
cies in the color balance. By holding 
the proper filter of the right density over 
either the original patch or the printed 
one, as the case may be, and examining 
the result over a constant light source, 
the two gauges can be made to match. 
It is then easy to judge as to what 
change in the filter pack should be made. 
If the original was made to match the 
print, then a subtraction must be made 
from the pack, but if the print was 
made to match the original, the pack 
will need a filter added to it. Of course, 
a great deal will depend upon the 
technician who is handling the matching 
problem and considerable experience is 
necessary before consistent results are 
possible. Even as a cameraman allows 
his judgment to influence his exposures 
regardless of meter readings, so must 
the lab man make his decisions in the 
light of his past experiences. The 
system works very well in our laboratory 
and should certainly operate elsewhere 
with the same good reliability. 

Production for Television 

Even the smallest studio outside of 
metropolitan areas will find that sooner 
or later it must have some type of 
machine processing for black-and-white 
films if it is going to make television 
deadlines. There is no adequate proc- 
essing service in New England and 
we found much of our profit being 
disbursed in messenger fees, plane 
fares and 'phone calls not to mention 
the wear and tear on the nervous system. 
A simple, but very efficient processing 



machine for negative and positive 
processing is made by the Bridgmatic 
Company and we have found ours very 
satisfactory for the volume of work we 
have to do. Later models of this 
machine have incorporated a number of 
advantages including refrigeration units 
for cooling, but ours is the simplest 
model employing four 10-gal tanks, a 
dry box and a trouble-free film transport 
system. The machine has its limitations, 
of course, but with proper handling it 
does a fine job. For cooling we installed 
a window air conditioner controlled by 
a room thermostat and our processing 
quarters are small enough to keep 
everything, including solutions, at the 
proper temperature. For heating, pieces 
of Calrod strip were attached to the 
tanks which are also controlled by 
thermostat. We did find it desirable to 
increase the strength of the average 
hypo solutions about one and a half 
times to obtain complete clearing. 
When processing certain emulsions such 
as Eastman Kodak negative 5230 and 
5240, even this intensified hypo solution 
fails to do a good job of clearing if more 
than 4000 ft of film has been processed 
in it; in which case, hypo is also used 
in the short stop tank. 

Our particular machine uses steel, 
rubber-coated tanks and we have found 
it desirable to recoat them every six 
months with Du Pont Fairprene cement. 

The problems of the small motion 
picture studio and laboratory might 
well seem unsolvable to those who have 
gone many years beyond that stage of 
development, but I am sure that men 
and women who have been through the 
early stages, no matter where they find 
themselves today, will sympathize and 
appreciate what is being done in small 
quarters all over the country. Only 
those who have been set down in the 
midst of all the highly specialized ma- 
chinery, the glory of the motion picture 
business today, may find us hard to un- 
derstand. However, the small producer 
is here, I am sure, to stay. 



Read and Bunting: Small Motion Picture Studio 



27 



Direct-Reading Light Flux Meter 



By G. GAGLIARDI and A. T. WILLIAMS 



The meter described in this article will measure the total lumens output of 
the projector and, by means of aperture plates, the light distribution over 
the screen. These measurements are taken by holding the meter directly 
in front of the projection lens. The "off" projector can be checked and 
adjusted just prior to use. 



I JURING THE PAST ten or fifteen years 
considerable work has been done by 
the Society to obtain satisfactory meters 
which would measure screen illumina- 
tion and brightness. Theoretically, the 
problem is not difficult but in practice 
the resulting meters are either too 
difficult to use or too expensive to be 
practical. This is particularly true in 
the case of a satisfactory brightness 
meter. Several satisfactory illumination 
meters have been described and used. 
In the March 1 948 JOURNAL the Screen 
Brightness Committee recommended a 
procedure of measuring the illumination 
by means of a visually corrected foot- 
candle meter. This procedure necessi- 
tated taking illumination measurements 
at five points on the screen and from 
these five foot-candle values a weighted 
average is calculated which, when 
multiplied by the effective screen area, 
in square feet, equals the lumens on the 
screen. This procedure often entails 
the use of extension poles in connection 
with the photocell targets or the use of 



Presented on May 2, 1951, at the Society's 
Convention at New York, by G. Gagliardi, 
Warner Brothers Theaters, Newark, N.J., 
and A. T. Williams, Weston Electrical 
Instrument Corp., Newark 5, N.J. 



ladders and precarious climbing on the 
part of the observer in order to reach 
the center and top of the screens. Some 
of the screens in drive-in theaters are 
so large that balloons have been used to 
lift the photocell to the high spots on 
the screen. At best it is a long procedure 
and one that can be done only during 
off hours. In drive-in theaters it can 
be done only after the last show because 
of the high ambient light at any other 
time. 

The new instrument, described later, 
was developed to measure the total light 
output of any projection system, and the 
side and center illumination, without 
leaving the projection room. All of 
these measurements can be obtained 
readily and quickly during show time 
and without causing any interruptions. 
The measurements are taken under 
actual operating conditions and include 
working parts, filters, lenses and shutters. 

Light Flux Meter 

The Light Flux Meter shown in 
Fig. 1 consists of three basic parts: the 
integrating chamber which contains 
the photocell, the meter mounted in a 
case containing the selector switch and 



28 



July 1951 Journal of the SMPTE Vol.57 




Fig. 1. Light Flux Meter. 






Fig. 2. Aperture plates. 



attentuating resistors, and a series of 
aperture plates to measure both total 
lumens and light distribution on the 
screen. All of these values can be 
measured in the projection room. 

The integrating chamber should 
theoretically be a large sphere with a 
small aperture but this is impractical 
for this application because such a 
sphere would be unwieldy and would not 
fit in front of the projectors in many 
booths. The integrating chamber used 
in this design actually consists of a 
hemisphere having an inside diameter 
of approximately 4 in. and a short 



cylindrical tube which joins the hemi- 
sphere with the two diffusing glass 
windows. The inside surface of the 
hemisphere and tube is coated with a 
lacquer having a white matte finish 
which produces excellent light diffusion. 
The location of the photocell and proper 
baffling to prevent direct light from 
striking it were carefully worked out 
with the result that the errors due to 
using various sizes of projection lenses 
are quite negligible. 

The photocell is a dry disc barrier- 
layer cell and is equipped with a filter 
which corrects it to the standard lumi- 



Gagliarcli and Williams: Light-Flux Meter 



29 



nosity curve as specified by the Inter- 
national Committee on Illumination. 

The meter is a permanent magnet., 
movable coil type of microammeter 
having two scales calibrated 0.0 to 15.0 
and 0.0 to 7.5 kilolumens. A selector 
switch allows the choice of either range. 

The aperture plates, shown in Fig. 2, 
serve two purposes. The aperture plate 
containing five circular perforations is 
used when the total lumens are to be 
measured. These holes are located in 
such positions on the plate as to simulate 
the five screen reading method recom- 
mended by the Screen Brightness Com- 
mittee. The total area of the five per- 
forations equals one-tenth of the area 
of a standard film aperture. The indi- 
vidual area of each perforation was 
graded in an attempt to give them the 
same weighting effect as the committee 
recommended. The center hole was 
made twice the area of one side hole and 
four times the area of one corner hole. 
In addition to the weighting effect, 
the aperture plate, because of its 10% 
transmission, reduces the temperature 
to safe values on the lens and on the 
integrating chamber and photocell. 

A single-hole plate is used to measure 
the relative light at the center of the 
screen and similar single-hole plates 
with the holes at the corners or edges 
can be used to measure the relative light 
values at other corresponding areas of 
the screen. These readings can be used 
to indicate relative illumination values, 
or the foot-candles can be readily 
computed by means of a simple formula. 
For example, if we make the hole 
diameter on each single-hole plate such 
that the area of the hole is 5% of the 
total area of the film aperture then the 
light intensity on any screen can be 
calculated. The light intensity, or foot- 
candles (7) will be a function of the 
screen size but since the ratio of screen 
height and screen width is a constant 
the screen areas will be proportional to 
the screen width squared (W 2 ). By 
measuring the lumens output (L) with 



the single-hole aperture plate in the 
film gate and the effective screen width 
( W] the light intensity can be calculated 
by the following formula 



Foot-candles 



2.74L 
W* 



In the above formula a 5% area plate 
was assumed. If it is desired to round 
out the formula then instead of using a 
0.1775-in. hole, which is the 5% area 
size, the hole diameter can be decreased 
to 0.1697 in. which will have 4.58% 
of the total area of the film aperture. 
In this case the formula will be as 
follows: 

Foot-candles = ^ 2 

Fifteen theaters were surveyed using 
this Light Flux Meter. Values were 
also obtained by using a foot-candle 
meter and calculations as described in 
the Report of the Screen Brightness 
Committee in the March 1 948 JOURNAL. 
Based on tests both in the laboratory 
and in the field with lenses of different 
focal lengths and different speeds, it was 
found that the maximum difference 
between the values obtained with the 
Light Flux Meter and the procedure 
specified by the Screen Brightness 
Committee was 8% but that the average 
was better than 5%. 

The advantages of the Light Flux 
Meter may be summarized as follows: 

1. All measurements can be made in 
the projection room. 

2. Measurements can be made during 
the performance on the "off" machine- 
without interrupting the show. 

3. Adjustments can be made simul- 
taneously with the measurements. 

4. Comparative measurements can be 
made quickly when any item of the 
equipment is changed. 

5. Check-up for peak performance 
may be made as often as desired without 
any extra expense or inconvenience. 

6. No external or internal source of 
power is required to operate the meter. 



30 



July 1951 Journal of the SMPTE Vol. 57 



Discussion 

K. Pestrfcov: Is the instrument available 
commercially? 

A. T. Williams: Unfortunately, it is 
not available. Our company is so tied up 
with war work that I doubt we could make 
one up. However, it is possible that some 
smaller company may take over the de- 
velopment and we are willing to turn over 
the design and the data that we have to 
some company that may do that. Mr. 
Gagliardi is working on that now. We 
would be glad to lend the instrument out 
for a reasonable time to anyone who 
wishes to do experimental work with it. 
We merely made this up in answer to a 
demand, but unfortunately, we are not in a 
position to manufacture it. 

W. W. Lazier: The Screen Brightness 
Committee would be glad to accept that 
offer and use the meter. Is there any 
way of taking into account the effect of 
the screen? That is the one link we lack 
after we have the incident illumination. 

Mr. Williams: No, unfortunately this 
does not consider the reflectivity or the 
polar characteristics of the screen surface. 
We merely measure the incident illumina- 
tion. 

R. H. Heacock: Is it put out in front of 
the projection lens? 

Mr. Williams: That is right. It is used 
right in the booth, and is put over the 
front of the projection lens. 

H. J. Benham: It would seem to me that 
the image would have to fill rather exactly 
the space that you had set aside to cor- 
respond to the projector aperture. Does 
that mean then that you move this device 
back and forth until you get it the exact 
size that fills the space you indicated on 
your little mask? 

Mr. Williams: No, the instrument is 
put directly in front of the lens. The 
mask is placed in the projector aperture 
itself, and therefore limits and defines the 
light passed on to the lens and the meter. 
Use of the integrating sphere enables the 
instrument to integrate correctly the in- 
tensities of the light beam irrespective of 
whether the projection lens has a focal 
length of 2^ in., 3 in. or 5 in., for example. 

Dr. Lo^ier: It will integrate a small cross- 
section beam as well as a large one within 
the diameter of the pickup element. 

L. Martin: I imagine a useful application 



of this meter might be the balancing of two 
or more projectors so that uniform bright- 
ness Is obtained when you change over 
from one to the other. Was it Mr. 
Gagliardi's intention to provide a meter 
that would be in continuous use during the 
show to keep the projectors properly bal- 
anced? Did your tests indicate why there 
are discrepancies in light output between 
projectors? 

G. Gagliardi: We have actually used it 
during the show in many instances. It is 
possible to take a series of readings from 
any projector at the end of a reel, after a 
change-over has been made. Only a few 
minutes are required for the readings, and 
possible adjustments, so that all projectors 
can be balanced without causing any inter- 
ruptions. 

This instrument could be used continu- 
ously or at periodic intervals in order to 
check the balance between projectors as 
well as their maximum output. Tests in 
the field indicated that most of our ma- 
chines were fairly well balanced. Dis- 
crepancies between projectors were usually 
traced to changes in carbon position or in 
relative position between lamphouse reflec- 
tor and projector aperture plate. 

In the shop or in the factory, where we 
made a lot of other tests, we were able to 
detect small differences in readings, de- 
pending upon carbon position, reflector 
position, changes in lenses and reflectors, 
and general equipment alignment. In 
other words, it was possible to tune the sys- 
tem to maximum output without looking 
at the screen, merely by looking at the 
meter. 

The choice of scale is something that can 
be determined later. We chose 7500 and 
15,000 1m because those values seem to be 
the mean and maximum output of the 
present projection systems with the shutters 
running. That is another thing you can 
determine: whether the shutter is set at 
50% transmission, or more or less. All of 
these things can be measured at your own 
convenience in the projection room if you 
wish to do so, or they can be measured any- 
where else for that matter. 

I know that in actual operation the 
readings of light intensity taken at the 
screen have varied widely. In order to get 
a decent average it may be necessary to 
repeat a set of five measurements several 



Gagliardi and Williams: Light-Flux Meter 



31 



times and average them, because you can- 
not depend on one reading alone. The 
new meter integrates and totalizes all the 
readings at once, so that the changes in the 
total value of light flux may be followed 
very readily. It is possible to follow the 
variation in light flux as the carbons are 
moved by the arc feed mechanism. 

Mr. Martin: Mr. Gagliardi's answer 
would indicate this is more a laboratory 
instrument for the initial adjustment of the 
projector than an instrument to be used 
constantly in the projection room in order 
to keep the projectors in balance during the 
performance. 

Mr. Gagliardi: I don't think that in most 
of our theaters you need to check the pro- 
jectors between each 20-min operation. 
However, you can use it as often as you 
please. 

Mr. Martin: I wasn't proposing that you 
do. I just wondered whether your measure- 
ments indicated any need for it or not, and 
I think you've answered my question. 

L. W. Davee: I have followed the work 
that Mr. Gagliardi has been doing for 
several years and I think that this instru- 



ment is the culmination of one of the finest 
pieces of work which has been presented be- 
fore this Society or in this industry for a 
number of years. I have been a very 
enthusiastic supporter of this development. 
This is not a piece of laboratory equipment. 
I believe it is a piece of equipment to be 
used by every equipment salesman and 
every dealer and every serviceman. I have 
nothing to do with selling these devices; 
I have no connection with them. I believe 
that the use of this meter, in other words 
the widespread use of this meter, will take 
some of the fallacies out of some of the 
sales stories a lot of salesmen in this country 
use in selling projection equipment, and I, 
for one, would like to see this meter adopted 
very, very widely. It would serve as a 
basis for comparison, it would standardize 
our industry, it would make our industry 
the type of industry I would like to see. 
As projector manufacturers, we would 
welcome such a piece of equipment on the 
market today so that we could come down 
to a basis for comparison of relative values 
of the equipment that is now offered to the 
theaters. 



32 



July 1951 Journal of the SMPTE Vol. 57 



New Processing-Machine Film Spool 

for Use With Either 35-Mm or 16-Mm Film 

By F. L. BRAY 



It was decided that a new film processing machine at Du Art Film Laboratories, 
Inc., should be capable of handling either 16-mm or 35-mm film. After a 
number of experiments to find the best sprocket and spool combination, a 
radically new type of spool distinguished by a tapered profile was chosen. 
The advantages of this design, as applied to sprocket-drive and friction-drive 
machines, are enumerated. 



w, 



HEN IT WAS decided that the new 35- 
mm developing machine being built at 
Du Art Film Laboratories should, if at all 
possible, be capable of processing 1 6-mm 
film interchangeably with the standard 
width, the general lines and type of de- 
sign had already been established. 

This machine was to have some 58 
spool banks of a type that is quite ortho- 
dox for a sprocket-drive machine. The 
top shaft is driven, and with it the film 
sprocket. The film spools on the top 
shaft are not secured to the shaft, but do 
have a tendency to rotate at the same 
speed as the shaft. The lower spools are 
all as free as possible on their shaft, and 
the carriage on which they are mounted 
is free to move straight up and down, but 
in no other manner. The weight of this 
carriage is supported entirely by the 
loops of film, which are thus kept in 
suitable tension regardless of the swelling 
and shrinking of the film as it progresses 



Presented on April 30, 1951, at the Soci- 
ety's Convention at New York, by F. L. 
Bray, Du Art Film Laboratories, Inc., 245 
West 55 St., New York 19, N. Y. 



through the stages of processing and 
drying. 

Tentative Approaches 

The first thought, probably, that would 
occur to anybody with this problem (of 
designing a dual-purpose processing 
machine) would be something like Fig. 
1A. It would be easy enough to recess 
the 1 6-mm portion of the sprocket deeply 
enough so that 35-mm film would bridge 
the 16-mm teeth with plenty of clearance. 
Of course the two kinds of film will 
travel at different linear speeds, but since 
all spools are idlers they will run at what- 
ever rotational speed is required of them. 

The technique of changing over from 
35-mm to 1 6-mm involves the use of an 
unperforated strip of machine leader 
tapered in width from 35-mm to 16-mm 
over a length of several feet. This is run 
through the machine slowly to make 
sure that the change-over is successfully 
accomplished. From the first we were 
willing to accept this step as practically 
unavoidable. 

Now, referring to the spool-sprocket 
combination of Fig. 1 A, we should note 



July 1951 Journal of the SMPTE Vol.57 



33 



Spools 



Sprockets 




+- 




Figure 1. 



that one serious difficulty threatened. 
In making a change-over, say from 35- 
mm to 16-mm, would not the film break 
immediately, due to the failure of the 1 6- 
mm sprocket to feed film as fast as it is 
demanded by the 35-mm sprocket ahead? 
No; actually the elevator would rise un- 
til the change-over is completed for that 
particular film bank. Moreover, a little 
analysis shows that the elevator rise 
would be exactly proportional to the 
reduction in linear film speed, with the 
result that the processing time remains 
unchanged. Of course, had this ar- 
rangement been adopted the productive 
capacity of the machine for 16-mm film 
would have been some 25% less, in 
feet per minute, than for the 35-mm size, 
and this might or might not have been 
regarded as a serious matter. 

The elimination of this elevator rise (or 
drop on going back to 35-mm film) might 
have been accomplished by using two 
sprockets having as nearly as possible the 
same pitch diameter, as shown in Fig. 
IB. This would have required manu- 
ally lifting the film from one sprocket to 
the other as the tapered change-over 
strip reached each successive pair. This 



operation would entail no great hard- 
ship, but would still take quite a long 
time to accomplish when, as in this par- 
ticular case, the machine was to carry 
some 7000 ft of film. 

It is not easy, nor would it be worth 
while, to recall all the proposals that 
were put forward and subsequently 
rejected. One of the more fanciful is 
shown in Fig. 1C. Here the idea was to 
have a pair of sprockets at the middle of 
each top spool shaft. One, the 35-mm 
driver, would be secured to the shaft, and 
contain a free-turning 16-mm insert 
without teeth. The other sprocket 
would be the 1 6-mm driver and would be 
fastened to a sleeve. This sprocket 
would in turn have had a pair of free- 
turning 35-mm rings. The sleeve was 
to be rotated slightly faster than the 
shaft, by means of a small speed-change 
gearbox at the end of each shaft, in order 
that both sizes of film should travel at the 
same linear speed. By this complex de- 
vice it was hoped that all the time lost in 
making a change-over might be saved. 

An Old Problem 

During the foregoing period of con- 
centration on sprocket design it was 
assumed that the spool would have to 
look about like those shown in Fig. 1, 
which are all the same. Now an ideal 
spool for 16-mm sound film seems never 
to have been made; so at about this 
point we began considering what kind of 
a compromise might be least objection- 
able for the 16-mm insert portion of our 
new combined spool. It is well-known 
that even very slight abrasions of the 
film base in the sound-track area can add 
noticeably to the ground-noise level of a 
16-mm sound track. Therefore what 
was sought in the 16-mm profile of this 
new spool was a minimum of support on 
the sound-track side that support to 
consist of soft rubber in contact with the 
very edge of the film base. 

Accordingly the idea illustrated in 
Fig. 2A was tried but it simply would 
not work. For when there was any con- 



34 



July 195 1 Journal of the SMPTE Vol. 57 




Soft Rubber Ban 



Figure 2. 



tact at all on the sound-track side, the 
film would be drawn up the steep rubber 
slope until it was almost entirely sup- 
ported on the sound track alone! This 
effect was conceived to be the same as 
that which causes a flat power transmis- 
sion belt to seek the high side of a 
pulley a principle that was subse- 
quently turned to good account. 

The next proposal for a 1 6-mm profile 
is shown in Fig. 2B. This soon had to be 
abandoned due to the difficulty of pro- 
curing the necessary quarter-round soft 
rubber in ring form. 

Toward a Solution 

About this time it became apparent 
that the whole idea of a composite spool 
with two different diameters might give a 
lot of trouble. In changing over from 
16-mm to 35-mm, for example, there 
would inevitably be a series of 18 sharp 
yanks on the film, each requiring the 
elevator to rise approximately one-half 
inch as the film climbed upward and out- 
ward from the 16-mm channel to the 35- 



mm channel of each successive spool. 
In the opposite direction, changing back 
from 35-mm to 16-mm it is hard to pre- 
dict what would happen, except that the 
operation would most certainly not be a 
smooth one. 

We were familiar with the belief held 
by some that a level soft rubber surface 
over the entire width of the spool, such 
as shown in Fig. 3A, is quite harmless to 
the support side of motion picture films, 
since the unit pressure between film and 
spool is held at a low uniform level in 
this way. However, because of a desire 
to eliminate every possible hazard, it was 
decided to positively relieve the picture 
area at least, and the sound-track area 
also if a way could be found. 

Equal Diameters, Yet Fully Relieved 

Out of all the above considerations and 
experiences, there finally evolved an 
entirely new film spool, the profile of 
which is shown in Fig. 3B. The most 
characteristic feature of this spool is the 
taper, which of course is an application 

16-Mm 
Track Perforation 



-35.3-Mm 


-* 


\ 


p 


Soft 

Rubber 


3 


Band 









U 




Soft Rubber Band 



Figure 3. 
F. L. Bray: Processing-Machine Spool 



35 



of the experience described previously. 
16-Mm film is threaded over this spool 
with the perforations toward the "high" 
side that is, the side with the larger 
diameter. In operation, the 16-mm 
film maintains the shape of a cylindrical 
surface, making contact only along the 
perforated margin. Moreover, this film 
always has a tendency to "climb" to- 
ward the high side of the spool until 
stopped by the guide flange on that side, 
at which position it is shown in the 
illustration. 35-Mm film, of course, is 
carried by this spool in the usual posi- 
tion, resting upon the shoulders on both 
sides. The 35-mm sound track may be 
at either side, as it will be fully relieved 
either way. 

While this spool has one apparent 
weak feature which will be discussed 
below it does meet every one of the 
objections heretofore encountered. It 
facilitates 16-mm production at full 
machine capacity. It fully relieves both 
the picture and the sound-track areas of 
16-mm sound film. And, most im- 
portant, it eliminates sudden slackness or 
yanks during change-overs. 

The weak feature referred to is that 
the weight of the lower spool assemblies 
(elevators) is supported entirely by the 
perforation part of the 16-mm film 
strands. While tests have shown that 
eight or even four strands are ample to 
carry this load, it has been learned by 
trial that the presence of any torn per- 
forations in 16-mm sound film must in- 
evitably result in breaks. For an answer 
it has simply been determined in advance 
that any 16-mm film fed into this new 
machine must be completely free of torn 
perforations. This is a quality standard 
which is considered well within the 
capacity of the laboratory. 

Operating Procedure 

In the interest of simplicity two sepa- 
rate, adjacent sprockets are to be used as 
in Fig. 3A and the changes will be made 
by hand. The hope is entertained that 
the operators will learn to catch the ta- 



pered strip as it passes each sprocket pair 
and to lift the film from one sprocket to 
the other without reducing machine 
speed. Otherwise it will be necessary, 
of course, to fill the machine with leader 
at the end of 35-mm operations, then 
change over to 16-mm leader before 
commencing 16-mm processing. Even 
in this case, however, thanks to the con- 
stant spool diameter, it will be possible to 
run the machine at full speed during the 
actual change-over, only stopping mo- 
mentarily at each sprocket, instead of 
having to run through 7000 ft at perhaps 
one-quarter speed. 

Design Features 

One or two of the details of this par- 
ticular design may be of interest. The 
purpose of the increased slope at the high 
side of the spool is to provide a definite 
break between the supported portion of 
the film and the relieved portion. The 
purpose of the soft rubber band is to 
provide a low unit pressure supporting 
surface for any 16-mm film which may 
temporarily come into contact with the 
middle portion of the spool. In addi- 
tion, this soft rubber, because of its rela- 
tively high coefficient of friction, assists 
materially in the steep climb required of 
the 1 6-mm film just before it reaches the 
shoulder on which it normally runs. 

The actual amount of taper selected 
for the spool is four degrees. A simple 
test showed that this value permitted a 
misalignment between the supply roll 
and our test spool of approximately one 
and a half degrees. That is, with any 
greater misalignment, 16-mm film started 
in the middle of the spool would not 
reliably climb onto the shoulder. An 
experimental spool having an eight- 
degree taper was also made, but had an 
incongruous appearance, and was only 
slightly superior in regard to ability to 
overcome misalignment. 

Another interesting discovery was that 
a little more misalignment is permissible 
at high linear film speeds than at lower 
ones. 



36 



July 1951 Journal of the SMPTE Vol. 57 



Use With Friction-Drive Machines 

This type of film spool may, it is hoped, 
be particularly applicable to friction- 
drive processing machines on which it is 
desired to run different film widths 
interchangeably. 

In the usual friction drive machine, 
the type of film spool shown in Fig. 1 
would be useless since, in changing over 
between the 35-mm and the 16-mm 
widths, there are no elevators to compen- 
sate for the difference in linear speed 
through the machine. 

Provided that tensile stresses, partic- 
ularly in the dry cabinet, are held within 



reasonable limits, there seems to be no 
reason why any friction-drive processing 
machine could not be readily designed or 
converted for satisfactory interchange- 
able service through the use of this new 
type of film spool. 

Discussion 

Gerald Graham: Are these spools on the 
market? Can you give us any informa- 
tion as to where they can be procured? 

Mr. Bray: They can be purchased 
from either the Luzerne Rubber Co., of 
Trenton, N.J., or from Du Art Film Lab- 
oratories. 



F. L. Bray: Processing-Machine Spool 



37 



Nonphotographic Aspects 

of Motion Picture Production 



By HERBERT MEYER 



Motion picture technology is predominantly focused on photographic and 
other processes for recording action and sound. Few papers 1 have been 
contributed dealing with other technical activities pursued with commen- 
surate skill, inventiveness and constantly expanding knowledge of materials 
and processes in Hollywood studios. Set construction and special effects 
present an amazing variety of problems little known or even suspected by 
outsiders as concerning motion picture production. This paper attempts 
a description of materials and techniques applying to set construction and 
special effects. Emphasis is placed on pointing out present technology, 
desirable improvements and possible developing trends. 



J_ ECHNICALLY, the motion picture 
industry is recognized and typed by 
its predominant and obvious activities 
in the use of photography as a means 
of recording and reproducing action and 
sound. For this reason, other tech- 
nological aspects which play a large and 
important part in the process of making a 
motion picture, are little known or recog- 
nized outside the studio. 

This paper attempts to point out the 
many processes and materials which the 
average motion picture studio employs in 
activities that are generally grouped 
within the broad functions of set con- 
struction. Considering that the studio, 
to furnish proper settings for story back- 
ground, must in the majority of cases 



Presented on April 30, 1951, at the So- 
ciety's Convention at New York, by W. 
V. Wolfe for Herbert Meyer, Motion 
Picture Research Council, Inc., 1421 
North Western Ave., Hollywood 27, Calif. 



construct and fabricate some or all of 
the sets instead of using existing locales, 
it becomes immediately apparent that 
the need for materials and fabricating 
methods in set construction is virtually 
unlimited and ever changing. 

The Motion Picture Research Coun- 
cil, 2 in recognition of this fact, has spent 
considerable time and effort in contact- 
ing literally hundreds of chemical and 
allied -material manufacturers and fabri- 
cators to obtain guidance and collabora- 
tion in finding new useful materials and 
processes applicable to this multifaced 
project. This has proved to be mutually 
beneficial, primarily for the reason that 
the contacted industries recognized mo- 
tion picture production, often for the 
first time, as a potential consumer of 
many of their products. The studios 
have profited substantially from these 
contacts since they provide a wealth of 
advanced technical information and 



38 



July 1951 Journal of the SMPTE Vol.57 



PRODUCTION MANAGEMENT 



ART DEPARTMENT 



SET CONSTRUCTION 



SCENIC 

PAINT 

PROPERTY 

CARPETING 

DRAPERY 



STAFF 

LUMBERMILL 

FOUNDRY 

PROP & MINIATURE 

CABINET 



HARDWARE 
MECHANICAL 
GREENERY 
POWDER & 

SPECIAL EFFECTS 



Fig. 1. Material-processing and fabricating shops and subdepartments. 



experimental aid contributed by the 
research laboratories and the highly- 
developed technical service divisions of 
practically all those enterprises which 
were approached. 

The set-construction department, to 
cope with the variety of tasks, has at 
its disposal an array of material-process- 
ing and fabricating shops and subdepart- 
ments which form an organized entity, 
as illustrated in Fig. 1. 

An exhaustive description of the func- 
tions and activities of each of these 
shops is not possible within the scope of 
this paper. Our discussion is restricted, 
therefore, to a presentation of typical 
examples. Before proceeding, a few 
remarks on certain features affecting set- 
construction operations may assist in 
better understanding existing conditions 
and the reasons for their establishment. 
Proper conception and analysis of these 
furnish means for recognizing future 
trends and form a basis for possible de- 
velopment in a desired direction. 

The fact that the studios should have 
to engage in such diversified fields of 
fabricating as indicated by the depart- 
mental setup, appears at first hand some- 
what debatable. The economic sound- 
ness of operating such shops can be 
rightfully questioned, assuming that 



within the large industrial area of Los 
Angeles there are a great many fabrica- 
tors who could take care of these require- 
ments and who operate with less over- 
head than the average studio. It can 
be shown, however, that the develop- 
ment of such industrial facilities is only 
of relatively recent date and not yet 
comparable to that of eastern and mid- 
western sections of the country. 

Another reason for the studios' policy 
of self-sufficiency in this field is the re- 
quirement of immediate availability of 
set-construction items. Scheduling a 
motion picture is controlled by many 
factors which, to a large degree, are 
not predictable. Changes in schedule 
are not introduced, as often assumed, 
by bad planning, but rather by the fact 
that even with the most careful and 
experienced preparation, last-minute 
modifications and delays are practically 
unavoidable. Production of a motion 
picture is, of course, a highly technical 
undertaking, but is interwoven with 
artistic and human elements which 
defy orthodox technical treatment. 
These circumstances necessitate rush 
orders which, in turn, require immediate 
availability of fabricating facilities in 
order to avoid expensive production de- 
lays. 



H. Meyer: Nonphotographic Aspects 



39 




Fig. 2. Typical hard flat set. 




Fig. 3. Rear view of hard flat, corner 
section, showing structural details. 



Furthermore, it is doubtful that 
outside fabricators could produce some 
of the properties at a profit within com- 
parative studio costs, since repeat orders 
are not guaranteed, quantities are small 
and the fabricated item does not always 
have a value for other markets. 

One may interject that there must be a 
number of items of repeated usage in 
set construction which consequently are 
practically standard in size and shape. 
An article of this type is the brick-wall 
unit which is produced in large numbers 
in studio staff shops. There is little 
doubt that with industrial advancement 
a substantial portion of present costly 
studio operation in fabricating will 
eventually be entrusted to outside local 
establishments to mutual advantage. 

Following is a description of activities 
pertaining to set construction. In view 
of the great variety of materials and of 
application methods, three main groups 
were selected: 



40 



July 1951 Journal of the SMPTE Vol.57 



I. Structural materials for sets and 
set properties and techniques of appli- 
cation; 

II. Materials and methods for sur- 
facing; and 

III. Materials and methods for 
"special effects." 



An attempt has been made to cover 
established practices, recent develop- 
ments and to indicate trends. It was 
thought important in this connection 
also to point out objectives which so far 
have not been satisfactorily reached. 



Part I. Structural Materials for Sets and Set Properties and Techniques 

of Application 

strength and bulk to be used as a wall unit 
without requiring heavy bracings. 



Wood Products 

Lumber, presswood and composition- 
type materials such as plywood, 
masonite, fiberboards and similar prod- 
ucts, are used in considerable quantity. 
A typical structural unit to be found 
in studio set construction is the so-called 
"flat." Two types of flats, both used for 
interior walls, are practically standard 
items. 

One, called "hard flat," is made of a 
multiple plywood surface backed by a 
wooden frame and bracings (Figs. 2, 3 
and 4). It serves as a wall unit of great 
durability, which is reused over and 
over again. It is fabricated up to sizes 
of 4 X 1 2 ft and is fairly heavy. 

The other type, called "soft flat" 
(Figs. 5 and 6), is composed of a light 
wooden frame over which is tightly 
stretched a muslin-type fabric. It was 
introduced originally by requests of the 
sound engineers for wall materials of less 
density than the plywood-surfaced flats. 

Both types have their specific advan- 
tages and disadvantages. The present 
trend, which favors hard flats, is due in 
large measure to the successful introduc- 
tion of the Peel Paste 2 technique with its 
improved method of recovering and 
resurfacing plywood flats. 

There is a definite interest in an 
improved hard flat, lighter in weight and 
more resistant to scuffing than plywood. 
It should be free from warpage, reason- 
ably weather resistant and permit nail- 
ing. The ideal would be a board 
material exhibiting all these properties, 
and, in addition, having sufficient 



Plaster Casting and Staff Shop 

Plaster-type materials are used in very 
large quantities and for a great variety of 
fabricating purposes. The low price of 
the raw materials and the simplicity of 
fabrication methods which may be per- 
formed without exacting and expensive 
mechanical equipment have made plas- 
ter casting a most important part of set- 
construction activities. Modern cost 
analysis of studio operations, however, has 
revealed that the excessive weight of 
plaster casts, which translates itself into 
high costs for transportation, supporting 
structures and rigging, causes plaster to 
be a highly expensive operational item. 
Low chip resistance, brittleness and poor 
weathering properties are also on the 
debit side. 

This has prompted the search for 
lighter-weight materials of greater me- 
chanical endurance, which has resulted 
in the introduction of plastics in direct 
replacement of plaster, as described in a 
later section. 

Many direct efforts have been made to 
eliminate the shortcomings of standard 
plaster casts, aimed at improvement of 
plaster materials as well as fabrication 
methods. 

Casting-plasters of highly increased 
tensile and impact strength, such as cal- 
cined plaster and melamine-compounded 
types, have not found appreciable recog- 
nition due to their much greater material 
cost. Art plaster, a dextrine-gypsum- 
type material, has been accepted for its 



H. Meyer: Nonphotographic Aspects 




Fig. 4. Construction of hard flat set. Front surface of set walls presents 
intricate ornamental patterns obtained by novel plaster casting technique. 




42 



Fig. 5. Typical soft flat set. 
July 1951 Journal of the SMPTE Vol. 57 




Fig. 6. Soft flat unit. Same as Fig. 5. rear view. 




Fig. 7. Arch cast from urea-formaldehyde-reinforced plaster. 
H. Meyer: Nonphotographic Aspects 



43 



noticeably better mechanical properties 
(except sensitivity to humidity), since it 
is available at only a fractional increase 
in cost per pound. 

Recently, the studios have found 
excellent use for urea-formaldehyde- 
fortified plaster. In the present form of 
application, this resin and the required 
catalyst are added in water solution to 
the plaster slurry. The greater tensile 
and impact strength of the resulting 
plaster is utilized in several ways: it per- 
mits thinner casts, which means reduction 
in weight; it has also been found suitable 
for replacing expensive wooden mold- 
ings, such as are required for the curved 
parts of Roman- or Gothic-type window 
frames; it has become a preferred 
material for building cornices, stairway 
steps and other structural units which 
may be exposed to excessive scuffing, 
marring or wear of any type (see Fig. 7). 



However, the hardening of plaster 
through admixture of urea-formalde- 
hyde is only effective to a certain degree. 
It was found that the hardening effect is 
practically confined to the surface of the 
plaster cast and that inside portions re- 
main unchanged. This is probably due 
to the fact that the gypsum in the process 
of setting squeezes the yet unreacted 
urea-formaldehyde solution toward the 
surface. The setting of the urea- 
formaldehyde to a resin apparently 
takes place later. It is, no doubt, in- 
duced by the increase in temperature 
resulting from the exothermic reaction of 
plaster setting. 

A more uniform hardening effect can 
be obtained by considerably increasing 
the amount of urea-formaldehyde added 
to the plaster slurry. However, this 
raises the material cost to an objection- 
able degree. 




Fig. 8. Rough-surfaced stone slab, 
spray-cast from mixture of chopped glass 
fibers and plaster slurry by Paralite 
process. 



Fig. 9. Rock column made from glass 
fiber-reinforced polyesters. Brick wall 
and stone wall units fabricated from same 
material. 



July 1951 Journal of the SMPTE Vol. 57 



Studies aimed at keeping the urea- 
formaldehyde more uniformly distrib- 
uted in the plaster cast through addition 
of water-soluble gums or cellulosic ethers 
show promising results. 

Hardening of plaster does not satis- 
factorily increase chip or crack resistance. 
Recent experimental work in this direc- 
tion has produced improved plaster 
modifications through incorporation of 
film-forming emulsions of polyvinyl, 
methacrylate, polystyrene and copolymer 
types. 

The reinforcement of plaster with 
fibers is generally practiced. Plant 
fiber, such as sisal, has been replaced in 
some studios by glass fiber, while others 
consider the higher cost and the irritating 
effects of glass fiber dust with disfavor. 

An ingenious method of spraying 
plaster slurry together with short chopped 
glass fiber into molds, using a specially 
designed double-spray gun, has been de- 
veloped by one of the studios. It is 
most advantageously applied in fabricat- 
ing large objects such as rocks, brick-wall 
paneling and other structural items, since 
it permits reduction of cross section and, 
consequently, weight, without sacrificing 
strength (Fig. 8). 

Mold Materials 

The flexible polyvinyl-type mold has, 
in several studios, practically taken over 
the function of the glue mold for plaster 



castings due to its superiority in tough- 
ness, flexibility, inertness to humidity 
change and other properties. It also is 
replacing increasingly the rigid plaster 
mold except when relatively very large 
castings are being made. Here the dif- 
ference in price of the mold materials 
and the ease of fabricating the mold may 
still favor plaster. So far, the thermo- 
plastic-type polyvinyl rubber is prac- 
tically unchallenged, in spite of the fact 
that it requires a rather critical process 
of heating, melting and pouring. The 
thermosetting type of material available 
for making flexible molds, such as thiocol 
rubber which can be worked at room 
temperature, is considerably higher 
priced and cannot be reused, so that 
mold failures are total losses. 

Plastics and Related Materials 
for Structural Use 

Thermosetting Compounds Polyester Con- 
tact Resins. The most significant change 
that has recently affected the established 
routine of studio staff" work was brought 
about through the introduction and 
acceptance of polyester contact resins. 
These compounds, activated by catalysts 
and accelerators, set up and cure at 
room temperature to yield rigid or flex- 
ible shapes of extreme mechanical 
strength and excellent detail fidelity. 
They have, so far, most closely answered 
the need of the studios for suitable light- 




Fig. 10. Roofing shingles cast in unit of 
approximately 4 f t x 6 ft, made from 
glass fiber-reinforced polyesters. 



Fig. 11. Same as Fig. 10, 
rear view. 



H. Meyer: Nonphotographtc Aspects 



45 



weight structural materials. The gen- 
eral technique by which they are em- 
ployed consists of a casting-laminating 
process which combines glass-fiber mats 
with the resin in rigid plaster or flexible 
molds. Final curing to tack-free sur- 
faces is obtained by exposing the cast to 
sunlight or through short heat cycles in 
temperature-controlled ovens. The ex- 
ceptional impact and tensile strength of 
these casts makes it possible to reduce 
their thickness to a fraction of that re- 
quired for plaster casts. This results in 
substantial savings in transporting, erect- 
ing and striking, so that in spite of the 
comparatively high material cost of 
polyester-styrene resins, their use has 
been constantly increasing (Figs. 9, 10 
and 11). 

Desirable Improvements in Polyester Con- 
tact Resins. Desirable improvements to 
extend the application range of these 
types of materials for studio work are ex- 
pected in the following directions: 

(a) Development of lower-priced resins: 
It is conceivable that progress in fully 
understanding the reaction mechanism 
of cross-linking polymers will extend the 
presently restricted number of relatively 
expensive unsaturated chemical com- 
pounds, such as alkyd types, to include 
less costly components possibly capable 
of forming thermosetting resins under 
proper conditions. Particular attention 
is pointed to the potential usability of 
the various unsaturated residues ob- 
tained in refining petroleum crudes. 
They are inexpensive and abundantly 
available. They form thermoplastic, 
low-molecular polymers when heated in 
presence of oxygen without appreciable 
loss of double bonds. Being usually of 
dark color limits their application in 
many fields. This would not, however, 
prohibit their extended use as structural 
materials in studio work, prpyided a 
simple reaction process could be devel- 
oped to change them into thermosetting 
compounds. ; 

(b) Development of fire-resistant-type 
polyesters: Although flameproof resins 



are commercially available, or treatments 
to reduce the flammability of standard 
types have been suggested, none of these 
are entirely satisfactory so far as studio 
experience has shown. Improvements 
in this direction would open additional 
avenues of application for these materials. 

(c) Improved parting agents for flex- 
ible molds: Since monomer styrene 
attacks polyvinyl chloride-type mold 
materials, particularly at elevated tem- 
peratures, difficulties are encountered in 
the use of such molds for polyester sty- 
rene casts and laminates. 

(d) Development of spray technique 
for polyester resins: Spray techniques 
are being used by a number of commer- 
cial fabricators, such as boat builders. 
A thoroughly satisfactory method has, so 
far, not been developed for application 
to studio work. The two principal 
difficulties concern the control of the 
catalyzed resin to avoid premature gel- 
ling in the gun and in the mold, and the 
poor wetting properties of glass fiber 
which prevent satisfactory penetration of 
the resin into the fiber mat. 

(e) Colorless, transparent casting resin 
of low shrinkage: Requests for such a 
material have long been voiced in vari- 
ous fabricating fields. There is a defi- 
nite, although limited, need for studio 
application. 

Miscellaneous Recent Developments in 
Thermosetting Plastics. Of possible sub- 
stantial importance appears to be the 
recent advance in producing cold- 
setting phenolics. Their properties are 
sufficiently different and distinct from 
those of polyesters that they should find 
many uses to good advantage. At this 
point, however, practical experience is 
yet insufficient for their full evaluation. 

A unique product employing polyester 
constituents has been successfully intro- 
duced for application in prop and minia- 
ture work. It consists of a special-type 
clay material impregnated with pre- 
catalyzed polyester-styrene. This com- 
pound can be hand formed or modeled 
since it has claylike properties, and can be 



46 



July 195 1 Journal of the SMPTE Vol. 57 



set and cured to a tough, rigid material 
by exposure to heat. 

Glass-fiber sheaths impregnated with 
precatalyzed polyester-styrene are known 
to the studios. Their use has, however, 
not been extensive. 

The recent commercial appearance of 
polyesters in solid form which are formu- 
lated by the user through the simple 
process of dissolving the solid in mono- 
mer styrene, is decidedly interesting. 
The advantages offered in safer storage 
and choice of formulation should make 
these resin types a welcome addition to 
the ones available as ready-to-use poly- 
ester-styrene liquids. 

Thermoplastic Compounds. The variety 
of materials belonging to this group does 
not lend itself to simple classification. 
Materials such as waxes have to be in- 
cluded although they may not belong, 
by chemical structure, to the group of 
plastics produced by polymerization. 
Some of these materials are employed in 
fabrication methods making use of their 
thermoplasticity, others are not. In the 
first instance, their thermoplastic proper- 
ties are a direct advantage, while in the 
second case this property is either ignored 
or presents even a disadvantage rather 
than an advantage. 

Of the many materials used quite 
extensively by the studios, the following 
were selected as examples: 

(a) Waxes: Natural and synthetic 
waxes have been found to offer unique 
properties in the fabricating of a number 
of different studio properties. Their 
peculiar translucency and surface reflec- 
tivity make them ideal for imitation of 
objects which depend upon these specific 
qualities for convincing photographic 
reproduction. The ease with which 
waxes can be colored or pigmented is 
another favorable quality. 

An outstanding field of potential 
application, not yet fully exploited, is 
that of marble imitation. It is repeated 
for emphasis that adaptability of ma- 
terials for studio work depends not, in 
the final end, upon visual, but on photo- 



graphic judgment. There is no material 
known comparable to waxes which con- 
veys, in photographic reproduction, 
equally the peculiar, complex impression 
of marble as it is stored in our memory. 
Fairly satisfactory marble effects are fre- 
quently obtained through surfacing ob- 
jects such as walls or panels with a marble- 
patterned paper, which is a simple and 
inexpensive process. This becomes, 
however, quite difficult when the surface 
of the object is of a compound shape or if 
the object has fine ornamental details 
and undercuts. Certain types of col- 
umns are good examples in this respect. 
Casts made of white microcrystalline 
wax, impregnated with dyes and pig- 
ments for imitation of veins and irregular 
strata, produce most striking effects. 

Different techniques for fortifying 
waxes to increase tensile and impact 
strength, through adding small percent- 
ages of ethylcellulose, low polymer-type 
polyethylene and other ingredients, make 
it entirely feasible to consider waxes for 
much more general structural use in 
competition with the already discussed 
thermosetting materials. Such modi- 
fied wax materials are already success- 
fully employed by commercial fabrica- 
tors in the manufacture of window-dis- 
play models, dolls and ornamental 
figurines. They can be used as such, or 
in combination with reinforcing materials 
such as fiberglas. A unique process for 
such purposes is slush molding, wherein 
the molten wax is poured into a closed 
female mold. After pouring back the 
excess, a hollow cast remains. The wall 
thickness of the cast can be controlled 
through adjustment of the pouring 
temperature. 

The relative flammability of wax 
materials presents a serious hazard during 
the process stage and in the finished 
product. The necessity of pouring the 
material at high temperatures contrib- 
utes, in addition, to the dangei of 
occupational hazards. 

(b) Thermoplastics for hot-drawing 
techniques: This standard process, 



H. Meyer: Nonphotographic Aspects 



47 



which requires only a minimum of 
simple and inexpensive equipment, is 
favored in studio prop and miniature 
shops for fabrication of a variety of 
items. Among these are helmets, ar- 
mors and similar historical commodities. 
The imitation of the required metallic 
properties is accomplished through sur- 
face treatment. In film productions of 
stories with a medieval historical back- 
ground, availability of this process pre- 
sents a highly appreciated contribution 
to economy and, not least, to comfort for 
the wearer due to the lightness in weight. 
Thermoplastic sheet materials, used 
for hot drawing technique, are methac- 
rylates, ethyl cellulose and cellulose 
acetate. Cellulose triacetate, recast from 
photographic film waste, and extruded 
cellulose acetate butyrate sheets are also 
presently under consideration. 

(c) Cellulosic materials specialties: A 
commercially available, highly porous 
material in sheet form, consisting of cotton 
flannel impregnated with cellulose ni- 
trate and a fire retardant, has been 
found quite useful for fabrication of 
lightweight articles such as boat hulls, 
cylinders, shells, tubes, guns and clubs. 
The original dry material is impregnated 
with a solvent and becomes entirely 
flaccid. In this condition it can be 
readily formed around or in a variety of 
regular or irregular shapes. Upon evap- 
oration of the solvent, the material be- 
comes rigid, retaining the shape formed 
during the molding operation. 

Similarly, it is possible to impregnate 
plain felt, gauze or paper with a solution 
of cellulosic materials and to obtain a 
practically equivalent result. 

Due to the fire hazards involved, sug- 
gestions have been made to replace the 
cellulosic components with polyvinyl 
resins. Some of the recently-tested for- 
mulations appear to work satisfactorily. 

(d) Cellulosic materials for translucent 
screens: The use of cellulose acetate and 
ethyl cellulose in the fabrication of large 
seamless sheets of up to 30 X 36 ft for 
background process screens, and of even 



considerably larger sizes for translucent 
scenic backings, are rather ingenious 
developments that originated in Holly- 
wood studios. Such sheets are fabri- 
cated by hand spraying a carefully 
blended mixture of cellulosic materials, 
plasticizers and solvents of varying vola- 
tility against a resin-impregnated canvas 
sheet serving as a matrix. This matrix 
is normally mounted overhead in a 
horizontal position. The spray opera- 
tion is continued until a sheet of sufficient 
uniform thickness is obtained. The 
finished sheet is stripped off the matrix 
and mounted with uniform tension onto 
a vertical frame. The required diffusion 
is obtained by hand spraying the sheet 
surfaces with a similarly formulated 
cellulosic dope, as was used for making 
the sheet, to which suitable diffusing 
agents, such as zinc stearate, silica gel or 
others are added in uniform dispersion. 

(e) Use of other plastic materials: 
From this report so far, it becomes evi- 
dent that the predominant use of plas- 
tics and other materials for structural 
purposes in a broader sense, centers in 
the fabrication of rigid articles and units. 
This accounts for the relatively small 
employment of vinyl-type materials in 
this field. 

Fabrication of flexible commodities is 
mainly represented by sponge and foam 
rubber. Some of the studios have fully 
equipped facilities for processing such 
materials and have excellent knowledge 
in formulation and handling. 

The technique of using Plastisols has 
not yet found entry into studio shops. 
Cost of materials, initial equipment and 
operations are considered fairly prohibi- 
tive, since the studios are not concerned 
with mass production. Artificial plants 
and leaves are now commercially pro- 
duced from polyvinyls by a Plastisoi 
technique. Such a process, if applicable 
to the manufacture of bulk foliage, would 
be of extreme importance and interest to 
this industry (Fig. 12). 

Cold slush molding, using natural 
rubber latex and porous (plaster) molds, 



48 



July 1951 Journal of the SMPTE Vol. 57 




Fig. 12. Plastic plants and foliage fabricated from poly vinyl Plastisols. 



BBSC_JC...-I4E 

' [ ^a^^^-- 

.. ? 







Fig. 13. Unfinished brick wall made from "Thermold." 
H. Meyer: Nonphotographic Aspects 



49 



has, so far, not gained much notice, al- 
though it appears a well-suited process 
for studio application due to its simplic- 
ity and the fact that through varying 
the amount of clay fillers, lightweight 
articles ranging from flexible to rigid can 
be produced. 

An important and unique use of poly- 
ethylene resin is in the construction of 
compound-shape stair-rail easements. 
The stair rail is first cast straight. By 
reheating selected parts to about 250 F, 
they can be bent and set to any desired 
shape. 

Development Trends in Thermoplastic 
Materials. 

(1) Thermoplastics, so far, have not 
been seriously considered or used as 
components in bulk structural materials. 
This possibility appears quite intriguing 
for the reason that a number of such 
materials, like asphalts, petroleum resins 
and pitches from various sources, are 
amply available at low cost. The fact 
that thermoplastics can be reused or re- 
shaped are added inviting properties. 

Their greatest deficiencies lie in lack 
of tensile strength and in their high 
brittleness which those exhibit that 
possess a softening point sufficiently high 
for studio requirements. 

It appears possible that these undesir- 
able properties can be sufficiently over- 
come through compounding with a rela- 
tively small percentage of rubber-type 
materials. It may be practical to fabri- 
cate sheets of varying stiffness through 
impregnation of textiles and other sup- 
porting materials with these modified 
thermoplastic compounds or to obtain 
them in calendering operations. One 
commercially available product of this 
type, although not known in composi- 



tion, has found use in the making of 
lightweight, brick-faced wall units (Fig. 
13). This material is supplied in rolls. 
When heated to an approximate tem- 
perature of 140 F, it becomes sufficiently 
pliable to respond to hand or low-pres- 
sure molding. Upon cooling, the molded 
material will regain its rigidity. The 
original commercial function of this 
material is to serve in the fabrication of 
dress forms which can be molded 
directly by hand over the human body 
due to the relatively low temperature 
required. 

It should not be assumed from the 
above that thermoplastic materials are 
considered a cure-all for the solution of 
the many structural material problems 
confronting this industry. However, an 
open-mindecT approach to the possibili- 
ties and advantages these materials 
unquestionably offer may pay consider- 
able dividends. It should be kept in 
mind that deficiencies in certain proper- 
ties, which would condemn such ma- 
terials for permanent structures, may not 
eliminate their usability for temporary 
structures in studio work. 

(2) An entirely novel approach, the 
practicability of which still awaits con- 
siderably more testing, suggests the use of 
unsupported polyvinyl sheetings as build- 
ing materials for relatively large props 
and structural units. These could be 
cut in accordance with designed patterns 
and joined by a heat sealing technique. 
For use, the finished article is inflated 
with air. The advantages offered are 
low weight and ease of transportation 
since props of this type can be deflated. 
This technique would also, of course, be 
practical only for a limited range of 
structural set items. 



Part II. Materials and Methods for Surfacing 



The activities related to this subject 
are performed by the paint shops and 
the scenic departments. It is a field in 
which the well-known techniques of 



brushing, spraying, dipping and troweling 
are applied with a variety of materials 
for ornamental and functional use too 
large to be described in. detail. 



50 



July 195 1 Journal of the SMPTE Vol. 57 



It includes oil- and water-base paints 
for outdoor and interior use, varnishes, 
lacquers, sealers, primers, thinners, sol- 
vents, protective coatings, flameproofing 
compositions, water repellents, flatting 
agents, pigments and fillers, surface- 
active agents, antistatic agents, wood 
preservatives, specialty coatings such as 
multicolor paints and skidproof paints, 
metallizing paints, conductive coatings, 
heat-absorbing and reflecting coatings, 
peelable coatings, adhesives, putties and 
caulking compounds, paint removers, 
floor maintenance compounds, cleaning 
compounds and a host of others. 

This general classification should suf- 
fice to convey an impression of the 
variety of materials belonging to the 
broad fields of surface treatment in 
which the motion picture industry is 
interested. 

Each paint shop has ample facilities 
for testing the constant flow of new com- 
mercial products to stay abreast of the 
rapid technical developments in all 
branches of interest. 

While it is not intended to describe 
surfacing materials and techniques in 
any detail, a brief consideration of some 
rather unique studio applications may 
be of interest. 

Outdoor Backings 

To the standard implements of studio 
facilities belong large rectangular-shaped 
pools which permit staging of any kind of 
water scene on the studio lot. The 
proper pictorial background, whether 
horizon and sky with cloud effects or 
other suitable scenery, is furnished by a 
hand-painted backing. The supporting 
structure for this painted backing is a 
wall made of plaster, concrete or wood. 
It presents a smooth, plain surface facing 
the pool. The background scenery is 
either painted directly onto this surface 
or the surface is first covered with canvas 
to which the paint is then applied. Out- 
door backings of this type are made up to 
sizes of 60 ft in height and 300 ft in 
length (Fig. 14). 



Surface coatings and paints suitable 
for this specific application require a 
high degree of weathering resistance. 
The use of polyvinyl derivatives which, 
when incorporated in a water-base 
paint, are capable of forming a tough, 
continuous film upon drying, has been 
recognized as an excellent means of pre- 
venting cracking and chipping of painted 
backings, even under prolonged expo- 
sure. 

Foliage Treatment 

The studio demand on cut branches or 
foliage for scenic effects is extremely 
large. Wilting and drying not only 
cause problems of fire hazards, but also 
necessitate continuous costly replace- 
ments. 

Two practical methods have been de- 
veloped and are in use, both capable of 
preserving foliage for repeated use and of 
rendering it effectively flameproof. 

One is a treatment by which the foliage 
is impregnated with a concentrated solu- 
tion of calcium chloride in large studio- 
designed vessels under application of 
vacuum and pressure (Fig. 15). The 
treated foliage loses its natural color, 
which is artificially replaced by means 
of spray painting with a coating con- 
taining a suitable dye and a flame re- 
tardant. 

In the other method, the foliage is 
simply hand sprayed with a formulation 
of natural rubber latex to which pig- 
ments and flame-retardant fillers have 
been added. 

Both methods have proved satisfac- 
tory in reducing fire hazard and prevent- 
ing drooping and wilting effects on 
leaves and branches by supplying a type 
of mechanical support to the treated 
foliage. 

Developments and Trends 

Modified phenolics formulated as 
sealers and top coatings have been found 
most useful for stage-floor maintenance 
and as protective coatings on plywood 
surfaces. 



H. Meyer: Nonphotographic Aspects 



51 




Fig. 14. Outdoor backing with built foreground set. 




Fig. 15. Plant and equipment for preserving and flame proofing 
natural cut foliage. 

July 1951 Journal of the SMPTE Vol. 57 



Hot spray lacquers are being tested for 
the advantages they offer in yielding 
heavier coatings. 

A trend toward water-base, latex-type 
paints is becoming quite evident and has 



just recently received considerable ac- 
celeration through the introduction of 
several polyvinyl-type products of greatly 
improved flow characteristics, stability 
and hiding properties. 



Part III. Materials and Methods for "Special Effects' 



Studio terminology combines under 
"Special Effects" a large variety of 
items, materials, equipment and processes 
which, selected and developed, some- 
times with amazing ingenuity, aid in re- 
alist'cally imitating natural phenomena 
for photographic reproduction which 
otherwise could be considered only at 
prohibitive expense or with impossible 
hazards. Some of the effects described 
belong to prop and miniature shop ac- 
tivities or those performed by the staff 
shop. 

The special effects department is con- 
stantly confronted with requests for the 
apparently impossible and actually creates 
new effects almost in every day's work. 
It is, therefore, possible to discuss only a 
number of those effects which have be- 
come standard parts of motion picture 
practice. Since this paper is written 
primarily from the viewpoint of one 
interested in materials, the purely 
mechanical phase of this field will also be 
omitted. It should, however, be men- 
tioned here that the efforts and merits of 
the special effects departments in engi- 
neering developments are outstanding in 
quality and quantity. Wind and wave 
machines, rain-producing equipment, 
explosive devices, instruments for any 
conceivable sound effect and innumer- 
able other means for producing specific 
phenomena in any wanted strength and 
modification give ample testimony to the 
inventiveness and mechanical skill of 
those engaged. 

Fog Effects 

In producing fog effects, the potential 
scope of fog-producing reactions, ma- 
terials and processes is considerably 
limited since toxic and corrosive ingredi- 



ents are prohibited. Other factors re- 
ducing the choice of materials are odor, 
lacrimating and otherwise irritating 
effects on personnel, and attacking prop- 
erties on paints, lacquers, textiles and 
the like. 

The most desired qualifications for 
fog effects are high volume, density, 
stability and, partly related, ease of 
stratification. 

The studios differentiate between 
chemical and other fogs. Chemical fogs 
are mainly those obtained by the inter- 
action of amines and acids, but also in- 
cluded are titanium chloride, sulfuric 
anhydride and other hydrolyzable com- 
pounds. They are known to produce 
fogs of ideal density, so far not obtain- 
able with any of the other materials. 
Corrosive properties, however, restrict 
them to occasional outdoor use. 

Oil fogs are most frequently used, al- 
though their density and stability are not 
too satisfactory except where large-size 
generators are employed. Oil fog is 
produced by studio-designed equipment, 
based on either atomizing oils selected 
from suitable petroleum fractions at room 
temperature or on vaporizing the oil by 
heating it to the required temperature. 
The latter process is quite superior where 
fogs of large volume and density are re- 
quired. It may be engineered by the 
simple use of electric hot plates or with 
complicated heat guns from which the 
oil is ejected by air pressure through 
nozzles after passing an arrangement of 
heat coils. Natural and dry ice are 
employed to increase density and sta- 
bility of the formed fog cloud. 

Developments in this field are aimed 
at improved equipment and simplifica- 
tion of producing methods. Recent 



H. Meyer: Nonphotographic Aspects 



53 




Fig. 16. Interior stage set with dress snow using crushed rock. 




Fig. 17. Interior stage set with dress snow using silica gel. 
July 1951 Journal of the SMPTE Vol.57 



experimentation with emulsified oils is 
quite promising. Investigation of 
humectants, such as glycol derivatives, 
with incorporation of inorganic salts 
such as ammonium chloride, point to 
other interesting material sources. 

Smoke Effects 

It is probably surprising to learn that a 
completely satisfactory method of pro- 
ducing black smoke is still not available 
or known to the studios. Of the two 
methods most frequently employed, one 
consists of the use of commercially avail- 
able smoke candles. These usually con- 
tain hexachloroethane, among other 
ingredients, and are disliked due to odor 
and corrosiveness of the smoke by- 
products. 

The other method makes use of a 
mixture of diesel oil with 30 to 40% car- 
bon tetrachloride which is ignited in 
open vessels. The function of the car- 
bon tetrachloride is to induce and main- 
tain conditions favoring incomplete com- 
bustion. Attempts to replace carbon 
tetrachloride with organic halogen deriva- 
tives of similar functional properties, but 
yielding less toxic decomposition prod- 
ucts, have so far failed. 

A limited, but occasionally pressing 
demand exists for colored smokes. Com- 
mercial smoke candles are available for 
this purpose but their performance is 
quite poor. Further research in aerosol 
technique, although so far not successful, 
may yet lead to better methods. 

Indications are that military basic re- 
search undertaken during the last war 
has advanced the knowledge of condi- 
tions under which controllable fogs and 
smokes can be produced to a remarkable 
degree. Much of this work still awaits 
declassification. 3 

Snow Effects 

Artificial snow for studio use has two 
distinct classifications. One includes 
materials useful for dressing stage or 
location sets with snow effects which are 
accordingly known as "dress snow." 



The other applies to material suitable for 
the imitation of falling snowflakes, which 
consequently is termed "falling snow." 

Materials for falling snow have to be 
fairly light, fluffy and of a particle size 
not less than f in. to properly convey 
photographically the impression of falling 
or drifting snowflakes. 

The same type of material used for 
falling snow may also be satisfactory for 
dress snow. However, dress-snow ma- 
terials generally consist of heavier, 
crystalline, salt-type compounds such as 
gypsum, rock salt and the like (Fig. 16). 

A recent interesting development con- 
cerning dress snow is a method by which 
a solution of sodium silicate and of a 
mildly acidic or alkaline compound is 
brought together to form silica gel in a 
reaction chamber consisting of an elon- 
gated cylindrical tube. The silica gel is 
extruded at the far end of the tube and 
chopped into snowlike fragments by a 
propeller blade. This process produces 
dress snow continuously. The equip- 
ment is mounted on a carriage which per- 
mits the dressing of sets and locations 
with a minimum of manual labor. This 
snow material is particularly capable of 
rendering realistic footprints and wheel 
tracks (Fig. 17). 

Another material, also lending itself to 
satisfactory rendition of snow impres- 
sions, is so-called "snow plaster" which 
has been in use by the studios as dress 
snow material for a long time. This 
product is specially produced casting 
plaster to which blowing agents have 
been added which are activated as soon 
as the plaster slurry is mixed. The re- 
sulting cast is a highly fluffy product 
which can be broken, crushed and pow- 
dered on fairly light impact. 

The oldest-known stand-by for falling 
snow material is a special type of corn- 
flakes. They are either thrown by hand 
into the air current of fans or sifted from 
overhead through sieves onto the stage. 
Rubber foam, feathers, heating of metal- 
dehyde, perlite, etc., have also been used 
more or less successfully for this. 



H. Meyer: Nonphotographic Aspects 



55 




Fig. 18. Equipment for producing falling snow with foaming agents. 



A novel process of great merit de- 
veloped in one of the Hollywood studios 
utilizes foaming agents in concentrated 
solutions such as have been employed in 
fire-fighting equipment. The solution is 
ejected in continuous operation through a 
rotating perforated drum mounted cen- 
trally in front of a large fan. The foam 
is propelled in controllable flake size 
over a relatively large area. Modifica- 
tion of fan speed permits a wide range of 
phenomena from light or dense plain 
snowing to blinding snow storms (Fig. 
18). 

The snow dressing of trees, slanting 
surfaces, window sills and the like re- 
quires, with present methods, a large 
amount of manual effort and is, there- 



fore, quite costly. A flocking procedure 
in some form, with suitable flock ma- 
terials, may be a future answer to this 
problem. 

In general, it can be stated that con- 
siderable savings would result if more 
suitable mechanical equipment for snow 
dressing and equally for removal of dress 
snow were available. 

As far as snow materials are con- 
cerned, none of the presently used com- 
pounds are entirely satisfactory. Color 
photography prohibits the use of impure 
salt materials. Some of the compounds 
affect clothing, paints and lacquers. 
Again, others lack stability in storage or 
while being exposed to outdoor weather 
conditions. 



56 



July 195 1 Journal of the SMPTE Vol. 57 



Cobwebbing Effects 

Spider-web imitation, a frequent scenic 
requisite for mystery-type stories is 
usually accomplished by spraying rubber 
cements using spray guns or special 
equipment with rotating ejectors for 
spinning the thread. Careful formula- 
tion is required to obtain realistic effects. 
Reasonable stability and nonflamma- 
bility of the formed web are desirable. 
Solutions of polyvinylidene chloride 
appear best suited. A quick solvent 
release through proper selection of 
solvents minimizes fire hazards. 

Breakaway Materials 

This designation is applied to struc- 
tural materials which, due to light 
weight, brittleness and other selective 
properties can be fabricated into fight 
props, such as clubs, sticks, gun butts, 
bottles and furniture and which on 
impact break easily without causing pain 
or injury. Such materials are also useful 
in the construction of buildings, walls 
and any type of structural unit which, in 
line with the story, collapses on the 
actors as the apparent result of catas- 
trophies such as earthquakes, ship- 
wrecks, bombings, etc. 

A further frequent use of this type of 
material is for the realistic replacement 
of window glass and mirrors. The hero 
or the villain involved in a barroom fight 
of an action-filled Western thriller may 
then endure safely the experience of 
being hurtled bodily through such props. 

The use of balsa wood for breakaway 
opaque objects dates back to the begin- 
ning of the motion picture industry. 
However, this material is quite expen- 
sive and is limited to typical woodwork- 
ing operations. Plaster extended with 
lightweight fillers such as vermiculite, 
perlite and ground Styrofoam has the 
advantage of being workable in molds. 
Foamed plaster, like the snow-plaster 
material mentioned earlier, is used more 
extensively. 

Just recently, commercially available 



gypsum, with a foaming agent added, 
has been found to permit the fabrication 
of porous, low-density molds particularly 
suitable for metal casting. The plaster 
slurry is beaten with a disc-like stirrer 
blade to entrain air and cause foam which 
can be made to consist of a very large 
number of bubbles of small, practically 
uniform size, evenly distributed through 
the slurry. Depending upon the amount 
of air entrained, the resulting cast ex- 
hibits different degrees of density. This 
material is also useful for casting break- 
away props. 

Various plastic compositions capable 
of being foamed in place have been 
tested without, however, so far finding 
suitable materials or processes. The 
only materials of proven reliability dur- 
ing the processing stage are the aryliso- 
cyanates, which are, at present, out of 
practical reach due to their high cost. 
Developments in this field of foamed 
plastics are eagerly awaited by this in- 
dustry as their potential usefulness in 
many applications is well realized. 

"Breakaway glass" can be made from 
a number of plastics, all thermoplastic 
by nature. The properties of these 
special compounds are quite tricky and 
include particularly a grade of brittle- 
ness which renders the material prac- 
tically useless for any other fabricating 
purpose. 

Breakaway glass props (Fig. 19) are 
made by slush molding or casting. The 
resins used should be preferably water 
white and transparent. The pour point 
should not be higher than 275 F; the 
softening point not less than 100 to 125 F. 
The resin must be free from cold -flow 
tendencies. It has to be friable and 
should readily break into fragments with 
completely dull edges. 

An ideal resin for this purpose was a 
specialty product manufactured by inter- 
nally plasticizing styrene with isoprene 
during the process of polymerization (re- 
versed rubber type). Unfortunately, 
this material is not produced any more 
for the present. Other materials quite 



H. Meyer: Nonphotographic Aspects 



57 




Fig. 19. Breakaway glass props. 



useful are special phenolic resins, aryl- 
sulfonamide-formaldehyde resins and a 
low polymerized styrene type plasticized 
with Aroclor. 

In instances where presence of color is 
not prohibitive (colored bottle glass), 
rosin can be used as an inexpensive, 
readily available material. 

The casting of panels serving as win- 
dowpanes is accomplished by pouring 
the resinous melt onto a sheet of cello- 
phane fastened to a wooden frame. 
The heat of the resin, upon contact, 
causes the cellophane to shrink and to 
furnish a taut, wrinkle-free surface. 
Cellophane, well known as a mold- 
release agent, permits safe separation of 
the highly breakable cast from its sup- 
port. One studio uses liquid mercury 
as a casting surface. Some of the liquid 
fluorohydrocarbons of high specific grav- 
ity and chemical inertness have proved 
experimentally useful for this purpose. 

The report given in the foregoing is by 
necessity sketchy. It has also been 
unavoidable to omit a number of other 
departments and their important and 
interesting activities and to by-pass de- 
velopment work in various phases of 



motion picture production of a non- 
photographic nature which this industry 
continuously performs. It is intended 
to cover some of these neglected subjects 
in a later paper. 

The following list of estimated average 
yearly requirements of the Hollywood 
motion picture industry on some of the 
macerials discussed may be of general 
interest: 

Plaster of Paris 3, 000 tons 

Casting plaster 85% 
Art plaster (plas- 
ter plus dextrin) 10% 
Hard wall plaster 
(calcined or 
resin additives) 5% 

Fiberglas 25 tons 

Natural fibers (mainly sisal) 50 tons 

Paint thinners 40, 000 gal 

Shellac 40, 000 gal 

Lacquer thinners .... 35 , 000 gal 

Paint lacquers 11 , 000 gal 

Flat paints oil base ... 32 , 000 gal 

Flat paints water base . . 15, 000 gal 

Paint enamels 6 , 000 gal 

Varnishes 4, 000 gal 

Whiting and titanox ... 20 tons 
Earth pigments and dry 

colors .... 95 tons 



58 



July 1951 Journal of the SMPTE Vol. 57 



Oil putty 

Spackling putty . . . . . 
Denatured alcohol .... 

Turpentine 

Linseed oil 

Carbon tetrachloride . . . 

Acetone 

Kerosene 

Stearic acid 

Floor wax liquid .... 
Floor wax paste .... 
Floor-cleaning compounds . 
Soap and detergents . . . 
Bronze powders 

Mold glue (gelatin) . . . 
Flexible mold materials 

(polyvinyl derivatives) 
Polyester-type plastics . . 



6 tons 

6 tons 

40, 000 gal 

10, 000 gal 

2, 500 gal 

7, 000 gal 

2, 000 gal 

10, 000 gal 

2 tons 

3, 000 gal 

3, 000 gal 

25 tons 

17 tons 

2 tons 

10 tons 

25 tons 
75 tons 



Lumber 

Plywood . 

Presswood 

Fiberboard 



20, 000, 000 board 

ft 

2, 000, 000 sq ft 
2, 000, 000 sq ft 
2, 000, 000 sq ft 



Textiles for backdrops, 
cycloramas, etc. (can- 
vas, cheesecloth, etc.) 2 , 000 , 000 sq ft 

Textiles for diffusion 
cloth (canvas, denim, 
nylon, etc.) .... 500, 000 sq ft 

According to the 1948-1949 Motion 
Picture Almanac, there are 276 different 



industries, arts and professions involved 
in the making of a feature. This same 
source lists the costs of "sets and other 
physical properties" for an average 
production budget as representing 35% 
of the total production cost. 

The Film Daily Year Book 1950 pub- 
lishes a figure of $62,874,000 covering 
Hollywood's 1949 bill for supplies, in- 
cluding maintenance costs. 

These few statistical estimates and 
facts may directly and indirectly sustain 
the statements made in the introductory 
part of this paper emphasizing the impor- 
tance and the extent of the nonphoto- 
graphic phases of motion picture pro- 
duction. 

References 

1. Barton H. Thompson, "Present an4 
proposed uses of plastics in the motion 
picture industry," Jour. SMPE, vol. 
43, pp. 106-114, Aug. 1945. 

2. W. F. Kelley and W. V. Wolfe, "Tech- 
nical activities of the Motion Picture 
Research Council," Jour. SMPTE, 
vol. 56, pp. 178-196, Feb. 1951. 

3. Handbook on Aerosols, U. S. Atomic 
Energy Commission, Washington, D. C., 
1950. 



H. Meyer: Nonphotographic Aspects 



59 



Improved Kodachrome Sound Quality 
With Supersonic Bias Technique 



By JAMES A. LARSEN 



By simultaneous application of signal frequencies, d-c noise reduction bias and 
"supersonic" a-c bias to a variable-density light valve, it is possible to make 
direct recordings or electrical prints on Kodachrome with very low inter- 
modulation distortion. This technique permits the use of a higher transmis- 
sion with a resulting increase in sound output of at least 6 db. 



E, 



ILECTRIGAL PRINTING of Kodachrome 
sound tracks without the use of high- 
frequency bias has been commercially 
available at least, on the West Coast 
for about two years. Intermodulation 
recordings made under these conditions 
indicated that for a modulation level at 
80% of clash, * the intermodulation dis- 
tortion was relatively high in the 
vicinity of 50% at densities that gave a 
usable volume. The reason that accept- 
able recordings were possible under such 
high intermodulation distortion was that 
the recording level was kept down allow- 
ing only an occasional peak to reach into 
the 80% or higher modulation level. 
This, of course, limited the level that it 
was possible to put on the Kodachrome 
electrical print. 

The advantages of "electrical print- 
ing" or re-recording printing of 16-mm 

Presented on May 4, 1951, at the Society's 
Convention in New York, by James A. 
Larsen, Academy Films, P.O. Box 3088, 
Hollywood, Calif. 

*Clash is the signal level into the light 
valve at which the light-valve ribbons just 
touch, or cross if they are not coplanar. 



sound tracks have been pointed out in an 
article by John G. Frayne. 1 Another 
article by C. R. Keith and V. Pagliarulo 2 
pointed out the advantages of using a 
high-frequency a-c bias in making black- 
and-white release prints using a direct- 
positive variable-density track. 

The method described herewith is a 
modification of the above-described 
methods of electrical printing and high- 
frequency bias direct-positive variable- 
density recording. In the present appli- 
cation, a high-frequency (24-kc) bias is 
applied simultaneously with signal fre- 
quencies and d-c noise-reduction bias to a 
variable-density light valve in the pro- 
duction of a Kodachrome sound track. 

This method produces Kodachrome 
prints having a higher output level and a 
greatly reduced intermodulation distor- 
tion of about 8%. This is equivalent to 
a harmonic distortion of approximately 
2%. In addition, greater density lati- 
tude or processing tolerance is obtained. 

The reason for the high intermodula- 
tion distortion in the old electrical print- 
ing process without high-frequency bias 
and its reduction by the new method 



60 



July 1951 Journal of the SMPTE Vol. 57 



Fig. 1. Transmission- 
exposure curves. 



using high-frequency bias can be seen by 
a study of the transmission-exposure 
curves shown in Fig. 1. In the lower 
curve, the large "hump" or lack of 
straightness is obvious. The straighter 
this curve, the better will be the repro- 
duction of sound and the lower the inter- 
modulation distortion. The application 
of 24-kc bias to the light-valve ribbons at 
approximately 200% modulation level 
has the effect of straightening out this 
curve of transmission vs. exposure as 
shown in the upper curve of Fig. 1 . The 
large hump is removed and the remaining 
curve is nearly straight. Under these 
conditions, intermodulation distortion 
(at the same level of audio modulation, 
namely 80%, and at the same density of 
the unmodulated track without noise 
reduction) was reduced from a value of 
56% without 24-kc bias to a value of 
about 8% with 24-kc bias. This very 
large reduction in intermodulation dis- 
tortion is due entirely to the straightening 
out of the transmission-exposure curve of 
Fig. 1. Comparative listening tests on 
musical recordings made with and with- 
out a-c bias confirm the results antici- 
pated by study of the transmission- 
exposure curves and the intermodula- 
tion curves of Fig. 2. 

It was found desirable to reduce the 
spacing of the light valve from the 
standard spacing (for 16-mm valves) of 
1.0 mil to 0.5 mil. Since the light valve 
resonates or is most sensitive to fre- 
quencies between 8,000 and 9,000 cycles, 
it takes a large voltage of 24 kc to drive 



PERCENT TRANSMISSION 

C 



































^^ 


^ 


""" 






Wl 


TH A-C 


IIAS-^ 


^ 


-- 












^ 


^ 


^ 


'/ 


-WITHC 


UT A-C 


BIAS 








_^**^* 






x- 


ALVE CL 


OSURE 


















-v 



+ 200 -200 

MILLIAMPERES - D-C BIAS (EXPOSURE) 



-WITH A-C BIAS 




WITHOUT A-C BIAS 



0.6 



1-0 1.4 1.8 2.2 2.6 

VISUAL DENSITY 

Fig. 2. Intermodulation curves. 



the light-valve ribbons to 200% modu- 
lation. Approximately 12 v of 24 kc 
was required. The 24-kc signal was 
obtained from a standard Model 200-A 
Hewlett-Packard audio oscillator. The 
24-kc level is set by measuring the output 
voltage of the oscillator with a vacuum- 
tube voltmeter, once the relation be- 
tween per cent modulation and voltage 
has been established. 

When the light-valve ribbons are 
modulated 200% by the high-frequency 
bias, considerably more d-c bias is re- 
quired to produce a given amount of 
noise reduction. The d-c bias must be 
sufficient so that, for silent passages, the 
light-valve ribbons are overlapped to the 
point where the peak amplitude of the 
200% modulation of the high-frequency 
bias slightly opens the ribbons. Refer- 
ring to Fig. 1 , it will be noted that with- 



J. A. Larsen: Sound on Kodachrome 



61 



out high-frequency bias, 250 ma of d-c 
bias reduces the average film transmis- 
sion from 27% to a minimum of 7.5%. 
This is equivalent to approximately 10.2 
db of noise reduction. With high-fre- 
quency bias, 250 ma of d-c bias reduces 
the average film transmission from 27 to 
16.5%. This is equivalent to 4.3 db of 
noise reduction. Consequently, in order 
to obtain 10 db of noise reduction when 
high-frequency bias is being used, a d-c 
bias of approximately 450 ma would be 
required. 

The two principal advantages of this 
method of electrical printing with a 24-kc 
bias over previous electrical printing 
methods are: (1) greatly reduced inter- 
modulation distortion as shown in Fig. 2; 
and (2) a large increase in volume from a 
variable-density track. In fact, it is 
possible to produce a variable-density 
track, using 24-kc bias, with very low 
intermodulation distortion and with a 
higher volume level than from a stand- 
ard, fully modulated variable-area 
track. Another less obvious advantage 
is the much greater latitude of Koda- 
chrome densities possible when using this 
method. If an arbitrary value of 10% 



intermodulation for an 80% modulation 
level is accepted as a practical operating 
condition, then the density range over 
which the intermodulation is 10% or less 
is between a visual density of 0.95 to 1.90 
(in the unmodulated area without noise 
reduction). In other words, any Koda- 
chrome density between 0.95 and 1.90 
will give a track with less than 10% 
intermodulation. Of course, the density 
of 0.95 will give much greater volume 
than the 1 .9 density and is therefore to be 
preferred. The relation between inter- 
modulation distortion and per cent total 
harmonic distortion is approximately 
4:1, so that 10% intermodulation distor- 
tion equals about 2.5% total harmonic 
distortion which is considered very good 
from a 16-mm Kodachrome film repro- 
duction. 



References 

1. John G. Frayne, "Electrical printing," 
Jour. SMPTE, vol. 55, pp. 590-604, 
Dec. 1950. 

2. G. R. Keith and V. Pagliarulo, "A 
direct-positive variable-density record- 
ing with the light valve," Jour. SMPE, 
vol. 52, pp. 690-698, June 1949. 



62 



July 1951 Journal of the SMPTE Vol. 57 



Tape Transport Theory and Speed Control 



By J. R. MONTGOMERY 



Absolute speed control can be achieved only with a fixed or recorded reference. 
Reasons include physical properties of tape and mechanical properties of tape 
transport. If tape properties can be accepted as they exist, the mechanical 
theories of tape transport must be thoroughly investigated. This paper is a 
resume of the pertinent and sometimes little understood phenomena of tape 
transport and a report of the limits which these theories have achieved in 
practice. 



I 



N THE LONG HISTORY of man's attempts 
to record the sounds he hears no 
problem has required more intensive re- 
search or provoked more discussion in 
technical circles than the efforts to con- 
trol both the instantaneous and long- 
term speed of the recording medium. 
The requirements of the radio broadcast 
industry created the impetus necessary 
to numbers of manufacturers and engi- 
neers who succeeded, after concerted 
efforts, in designing transcription turn- 
tables of sufficient quality to satisfy the 
minimum requirements of the broad- 
casters. The problems of rotating a 
surface at uniform speed were serious 
enough to evoke the wholehearted efforts 
of many of our highest-caliber scientists. 

Until a very few years ago most efforts 
to develop magnetic recording were 
conducted abroad. Indeed, most early, 
American tape recorder designs could be 
traced generically to the German "Mag- 
netophon." The magnetic recording 
art captured the imagination of a seg- 



Presented on May 4, 1951, at the Society's 
Convention in New York, N. Y., by J. R. 
Montgomery, J. R. Montgomery Engineer- 
ing Co., 1648 W. Haddon St., Chicago 22, 



ment of our engineering profession, but 
even more so, of our general population. 
As a result of this interest and the fact 
that the medium itself was no more per- 
fected than the equipment necessary to 
utilize it, the pressure for production 
caused hurried engineering and, in too 
many cases, insufficient research into 
the underlying theories of tape transport. 
The last two years have seen a shift 
toward sounder engineering. The prop- 
erties of the medium are now stabilized 
and, for the most part, understood. 
Standards of measurement and dimen- 
sion are more nearly established. The 
medium is accepted for use in its logical 
applications with general enthusiasm. 
Now we find ourselves in a position of 
having to return to a more fundamental 
philosophy of engineering to solve certain 
problems which have been clouded from 
view by the necessities of satisfying the 
initial demand for equipment. One of 
the greatest problems, as first presented 
by the broadcast industry and, of late, 
by the requirements of telemetering and 
other special applications, has been that 
old bugaboo speed control. This becomes 
understandable when one considers the 
proportionate numbers of moving parts 
in a magnetic recorder as compared 



July 1951 Journal of the SMPTE Vol. 57 



63 



with a disc recorder or playback table. 
One additional factor not seriously con- 
sidered by most designers was the con- 
cept of tape as an elastic medium. 

The general term speed control actually 
includes both long-period timing and in- 
stantaneous speed variations known as 
; 'wow" and "flutter." One of the odd 
facets of magnetic recording is the seem- 
ing ease with which moderate flutter can 
be produced. The methods necessary 
to idealize this performance are much 
more elusive. Speed control is relative 
to tolerances. The only known methods 
of controlling tape timing to milliseconds 
are by use of a fixed or recorded reference 
such as a recorded signal to operate a 
selsyn or other form of control over 
machine speed. If these tolerances are 
required, such complex and expensive 
methods are probably the best solution 
available today. If the tolerances re- 
quired are not closer than plus or minus a 
tenth of a second, the problem may be 
solved by purely mechanical methods, 
giving due consideration to the proper- 
ties of the various recording tapes and 
their limitations. 

The analysis of design theories and 
problems in magnetic tape recording 
may be arbitrarily divided into the 
following categories: 

The Recording Medium, 

Capstan Drive, 

Tape Supply, 

Pressure Pads Pro and Con, 

Take-up Design, and 

Integration of Design. 

The Recording Medium 

Two types of tape are generally avail- 
able, each having its own advantages and 
disadvantages. Paper-based tape has 
not been popular for professional use due 
mainly to surface finish. In order to get 
satisfactory signals from paper tape, 
pressure pads must be used to insure 
intimate contact of the oxide coating 
with the gaps of the magnetic transduc- 
ers. This is considered a disadvantage 
on broadcast equipment due to increased 



head wear. In addition, the measured 
signal-to-noise ratios are slightly inferior 
when using paper-based tape. How- 
ever, proper machine design can produce 
results from paper tape comparable to 
the average result now achieved with 
plastic tape on quality equipment. 

Paper tape has one distinct advantage 
for accurate long-term timing. It is not 
seriously affected by tension or humidity 
in such a manner as appreciably to 
change its length. Where the values of 
noise obtained from paper tape are 
acceptable, the speed-control problem is 
much simplified. In those applications 
where plastic-based tape is required, one 
must consider the elasticity of the me- 
dium and the effects of heat and humidity 
coupled with tension. Such tape, when 
wound tightly in a moist atmosphere and 
then dried thoroughly, may become com- 
pletely useless due to the stretching, 
warping, and multiple breakage which 
may occur while the tape remains in 
storage on the reel. These effects indi- 
cate the need for humidity control when 
close timing is desired. When the 
humidity is kept within a few per cent of 
a nominal, no appreciable errors should 
exist. Errors can exceed 5%, with a 
20% to 30% differential in humidity. 
In addition, the elongation of tape due to 
tension is aggravated by humidity. It is 
generally acknowledged that plastic tape 
may be easily deformed beyond its 
elastic limits. A fact often overlooked, 
however, is that momentary deformation 
short of permanent strain may be one of 
the most troublesome factors in the con- 
trol of average and instantaneous tape 
speed. For example, a tape which 
might be permanently deformed at 6-lb 
tension may stretch 1% or 2% momen- 
tarily with 3-lb tension and produce this 
percentage as "wow." This condition 
may also aggravate capstan control prob- 
lems which will be described later. This 
factor is the proximate cause of most non- 
periodic flutter in tape transport systems. 

Tape tensions measured by ordinary 
means are average tensions. Peak condi- 



64 



July 1951 Journal of the SMPTE Vol. 57 



tions may vary from this average by a 
factor of 4 : 1 or 5:1 on a well-designed 
machine under dynamic operating condi- 
tions. This condition, which we know 
to exist, creates the basic requirement of 
any tape drive: that the desired driving 
force must exceed the total friction in 
either direction by a factor of at least 
five, and preferably more. The corol- 
lary to this is that the maximum tension 
expected must never exceed that amount 
which will produce elongation when ex- 
pressed directly as a percentage and 
designated "flutter." These forces may 
be caused by drag, take-up tension, edge- 
guide scraping, bearing friction, rubber 
creepage, vibration and other transient 
and periodic conditions. The minimum 
tape tension is a factor of minimum in- 
ertia levels and satisfactory tape winding 
for storage and handling. 

Good practice would seem to indicate 
that the drag and take-up tensions should 
each equal a safe minimum for tape 
handling and the capstan drive should 
pull five times the maximum take-up 
tension. This procedure puts each ten- 
sion at its minimum safe value. Par- 
ticular care must be taken, of course, to 
prevent any uneven tensions, vibrations, 
or the rubbing of the edges of the tape on 
surfaces near the heads and capstan. If 
care is taken with the handling and stor- 
age of plastic tape and if machine ten- 
sions and design are reasonable, a satis- 
factory time-control condition may be 
obtained to a limit of less than 0.5 sec in 
1200 ft of tape. 

Capstan Drive 

Capstan drive is used almost uni- 
versally on magnetic tape recorders. 
This is due, in the main, to the ease of 
obtaining a constant single -surface speed 
(as in turntables) with the added ad- 
vantage of greater energy storage due to 
higher speeds. Most recorders now 
available have capstans which, in them- 
selves, can be manufactured to produce 
less than one tenth of one per cent "wow" 
or "flutter"; and which can, with syn- 



chronous motor drives, reproduce time 
to satisfactory tolerances for most pur- 
poses. At this point, however, most de- 
signs begin to experience difficulty. 
The problem is to couple the tape surface 
motion to the capstan surface in refer- 
ence to a transducer spaced some dis- 
tance from the point of capstan contact. 

Two general methods have been used; 
i.e., the friction surface and the pressure 
roller. The friction surface suffers from 
the necessity that the tape tensions must 
remain constant and of a certain mini- 
mum dynamic value, or the tape will not 
be driven at a given instant. These ten- 
sions, when adequate, become sufficient 
to cause the various phenomena previ- 
ously described and/or overdrive the 
capstan so as to cause slippage. The 
pressure-roller method is in more general 
use today. This method, however, 
suffers from certain pitfalls. The rubber 
surface, which is generally used, is under 
considerable pressure at the capstan 
against a small diameter. The surface 
speed of the rubber, therefore, changes 
sharply as it passes the capstan. If this 
rubber is substantially wider than the 
tape, the rubber surface will drive the 
tape and is driven by the capstan. Un- 
der this condition the creepage of the 
rubber under compression and motion 
influences the tape speed directly. As 
the diameter of the capstan and the 
durometer of the rubber are increased, 
this effect is decreased. At the same 
time, the driving friction between tape, 
capstan and rubber is materially de- 
creased, increasing the likelihood of slip- 
page. Under either extreme condition 
(and to a lesser extent between the ex- 
tremes), the tensions from both the sup- 
ply and take-up directions will influence 
the effect of creepage. 

When the pressure roller is not wider 
than the tape, the tape is controlled by 
the capstan surface and the only slippage 
factor is relative to tensions and not to 
creepage. The requirements of tape 
guiding generally make this method 
difficult to achieve due to tendencies for 



J. R. Montgomery: Tape Transport 



65 



the tape to walk out of the capstan. 
Also, the increased friction of bearings 
under greater side-loading pressures may 
often become a serious factor. In gen- 
eral, the use of as hard a rubber as fea- 
sible against as large a capstan as possible 
with good antifriction bearings on both 
members will produce the most satisfac- 
tory results. These results are then 
limited by the control of tape tensions. 

Tape Supply 

The total system drag friction as 
viewed from the capstan must be as uni- 
form as possible. Since the total must 
also be a fairly small quantity, the indi- 
vidual sources must be closely controlled. 
The loading effects of various amounts of 
tape on various sizes of reels must be 
minimized. The changes in tape path 
throughout a reel must not produce 
changes in tape-guiding friction. Par- 
ticular care must be taken to insure that 
the edge guides do not function by brute 
force to control the tape path, since the 
pressure of the guides on the slit edges 
can greatly increase transient tensions 
and can buckle the tape away from the 
heads requiring excessive pressure-pad 
tensions. The dynamic effects of the 
motion of both tape and reels must be 
damped to prevent periodic variations 
in tape tensions. Above, all, the axioms 
of tape tension ratios must be observed. 

Pressure Pads Pro and Con 

Two methods have been in general use 
to maintain coupling between the tape 
and the recording or reproducing heads. 
On professional machines using only 
plastic tape at high speeds, the combina- 
tion of supply tension and of the elastic 
moment of inertia of the tape have gener- 
ally been adequate to give satisfactory 
results. As tape speeds are decreased, 
this is not generally true. At 3.75 and 
7.5 in/sec the required longitudinal ten- 
sions on the tape to provide adequate 
coupling exceeds the safe tensions on 
either paper or plastic tapes, if flutter is 
considered. On such machines the high- 



frequency response can be greatly im- 
proved by the addition of light pressure 
pads at the gaps. The only deterrent to 
this procedure is the increase of head 
wear and, to some extent, of mainte- 
nance. For most applications the im- 
provement in performance is worth the 
inconvenience. 

When paper tape is used, pressure pads 
become almost mandatory due to the 
surface irregularities of paper tape. A 
simple rule of thumb to consider when 
not using pressure pads is that the useful 
tension at the gap is equal to the system 
drag tension times the sine of the 
angle of incidence at which the tape 
approaches the head, less the tape stiff- 
ness over extremely short lengths. 

Take-up Design 

Take-up systems may be divided gen- 
erally into two categories: the constant 
tape tension and the constant clutch- 
torque systems. Obviously, constant 
tape tension is more desirable from a 
theoretical point of view. On general- 
purpose recorders the choice is largely 
economic. If a common motor is used 
to supply power for a capstan and take- 
up, it is necessary to use a constant torque 
clutch in order to equalize the motor load 
and allow constant motor speed. This 
is because the power input to a clutch is 
the product of the speed of the driving 
member and the torque transmitted to 
the driven. If the tape tension is held 
constant, the driving torque required 
varies 4:1 on a 7-in. tape reel. If the 
torque is held constant, the tape tension 
will vary to the same degree. 

On professional-quality recorders the 
goal becomes constant tape tension with 
means of supplying power from a sepa- 
rate source. The methods used have 
varied from gravity-operated clutches, 
in which the weight of the tape controls 
the tension, to the design of special torque 
motors whose stalled rotor and slow- 
speed torque curves are complementary 
to the changes in tape-reel diameters and 
weights. 



66 



July 1951 Journal of the SMPTE Vol. 57 



An Integrated Design 

If the most desirable features for tape 
transport and speed control are com- 
bined, the result might well resemble the 
following description. 

The supply tension for the tape is pro- 
vided by a gravity-operated clutch of 
very light weight and a felt damping pad 
ahead of the recording head, plus a light 
pressure pad at the head gap. The 
total of this tension is maintained at be- 
tween 1 and 3 oz throughout the reel. 

The take-up tension is supplied by a 
gravity-operated clutch pulling the tape 
directly from the capstan at from 1 to 3 
oz of tension. A separate motor pro- 
vides power for take-up, transmitting the 
power to the clutch at a speed not ex- 
ceeding twice the maximum reel speed 
at the hub. 

The capstan is large in diameter (per- 
haps over 1^ in.). It is run on precision 
ball bearings with a ball thrust. The 
bearings are selected for both dimension 
and shock-excited noise. A synchronous 
motor drives the capstan through an 
idler or multiple-belt drive. The pres- 
sure roller is also large in diameter. It 
has a thick tire of hard synthetic rubber. 
It is approximately three times the 
width of the tape. The use of ball 
bearings is indicated here also. The 
path wraps the capstan at least 90 be- 
tween the heads and the pressure roller. 
Tension on the pressure roller is to be 
adequate to create an average pulling 
power for the tape of between 1^ and 
2 Ib. At this tension the rubber should 
not compress more than a few thou- 
sandths of an inch. 

If such a design follows good engineer- 
ing practice, it may be predicted that the 
long-term timing from the beginning to 
the end of a reel of tape will be main- 
tained within less than a half-second time 
deviation from the nominal, without the 
use of special synchronizing means. 
Actually one such device with several 
tape channels produces repeated timing 
of all channels within approximately -|- 



in. in 1200 ft on paper tape. This is 
equivalent to -fa sec at 7.5 in. /sec or an 
overall tolerance of nine millionths of one 
per cent. Tape measured on this ma- 
chine by the elapsed-time method is now 
a standard of timing for one of the 
national networks to allow equipment 
comparison between stations. 

When the flywheel or capstan itself is 
stable (neglecting tape coupling), the 
short-term flutter and wow should be de- 
pendably less than 0.15% rms, or 0.25% 
peak. As reference, it might be well to 
point out that this degree of stability is 
often obtained by manufacturers of com- 
petitively priced home recorders, up to 
the capstan surface. The poorer overall 
performance is generally traceable to the 
tape coupling and tension problems dis- 
cussed above. 

A recorder having these characteristics 
is suitable for most synchronous purposes 
where and when an absolute phase lock 
or absolute cue-in control is not neces- 
sary. In general, no difficulty should be 
experienced in using such tape for 
original preparation of movie sound 
tracks. With some of the editing pro- 
cedures now in use, even plastic tape 
would be feasible. On paper tape, re- 
sults could be better than one frame error 
in fifteen minutes. Admittedly, the pure 
mechanical approach to tape speed con- 
trol is limited to applications where half- 
second tolerances are generally satis- 
factory. It is felt, however, that the in- 
vestigation of basic principles has un- 
covered the possibility that many appli- 
cations, hitherto seeming impractical, 
may be solved without the expense of 
synchronous tape equipment. 
Acknowledgment 

The author would like to express his 
appreciation for the cooperation and 
encouragement over an extended period 
of time of the following people and organ- 
izations: L. S. Toogood, L. S. Toogood 
Recording Co.; R. T. Van Niman; 
Minnesota Mining and Mfg. Company; 
and National Standard Co. 



J. R. Montgomery: Tape Transport 



67 



Discussion 

Anon: The flutter at the capstan was of 
the order of 0.05%, as differentiated from 
the flutter at the head. I am wondering 
what measuring technique was used to de- 
termine the wow at the capstan? 

Mr. Montgomery: Various means have 
been used, such as stroboscopic observation 
of check points on the surface of the fly- 
wheel, means of building up systems which 
have practically no tension or inertia and 
achieving low wow and flutter measure- 
ments to that degree, using capstan drives 
to pull the tape. Those measurements, by 
the way, were made on a peak-to-peak 
basis, when related to actual measurements 
using tape, rather than on an rms basis. 

Dr. Kellogg: I remember a toy we played 
with in my youth, which consisted of a tin 
can and a string. You punched a hole in 
the bottom of the can, and threaded 
through it a piece of rather stiff string with 
a knot on the end, then rubbed the string 
with beeswax and rosin. When you pulled 
the string, you made a raucous noise, due 
to the intermittent grip of the fingers on the 
string. Perhaps a similar thing happens in 
tape machines, due to the friction of the 
tape on the magnetic head. Do you know 
of any indication that such a thing hap- 
pens? It has been rather difficult to 
account for the amount of high-frequency 
flutter. 

Mr. Montgomery: Any surface that the 
tape touches is bound to influence, to some 
degree, the driving friction of the tape. 
Since the tape is an elastic medium, if these 
tensions become at all appreciable, they are 
translated to the motion of the tape due to 
its elasticity. That has been a very serious 
problem with a great number of recorders 
and, for that reason, the manufacturers 
have tended to decrease the average run- 
ning tensions of the tape. Pressure pads 
can produce exactly the same type of 
problem and for that reason the tensions 



and the materials used in the design of 
pressure pads have to be considered in the 
light of the longitudinal pressures that 
they exert when the tape is in motion. 

Dr. Frayne: Concerning Dr. Kellogg's 
question, we have had opportunity over 
the past several years at Western Electric 
to measure flutter on a variety of tape 
machines. We find that most of them, 
when in good operating condition, have 
very good low-end flutter or wow. How- 
ever, on a flutter-measuring set which is 
capable of measuring side bands up to 200 
cycles, we often get rather abnormal values 
of flutter ; in fact, as high as one quarter of 
one per cent. If you employ a flutter set 
capable of measuring side bands up to only 
50 cycles, you omit the great bulk of the 
flutter frequencies. 

Mr. Montgomery: I might add that some 
work I was engaged in a while back shows 
that there was another factor that is quite 
often indicated as flutter, and which per- 
haps is indistinguishable from it in the effect 
on motion analysis. The effect magneti- 
cally perhaps may be described as incre- 
mental-time (phase) products due to d-c 
electrical and magnetic components, such 
as microscopic discontinuities in tape coat- 
ings and bias-audio composites, as instan- 
taneous values. To these must be added 
the side bands produced by any frequency 
modulation present. I don't know how to 
separate it from flutter in terms of measure- 
ment. I wish I did. It is that which we 
are prone to call modulation noise, which 
appears as side bands in that same range, 
quite often within a 200-cycle range of the 
fundamental and which produced, on 
most of your flutter-measuring devices, 
instantaneous changes in phase and in 
wavefront. Wavefront can confuse the 
flutter-measuring device so that you don't 
know which one you have. 

Dr. Frayne: The effect on the ear, I 
think, is the same. 



68 



July 1951 Journal of the SMPTE Vol. 57 



Television Studio Lighting Committee Report 



By RICHARD BLOUNT, Committee Chairman 



OVER A PERIOD OF YEARS the motion 
picture industry has developed lighting 
techniques which suit their modes of 
operation and, similarly, the techniques 
of the commercial still photographer 
have evolved to meet his requirements. 
It is not unreasonable therefore that the 
television industry, having borrowed 
some techniques from both groups, has 
gone on to develop additional methods 
to meet its peculiar needs. 

In order to facilitate this development 
the Society has formed this Committee, 
composed of engineering personnel from 
various television stations, people en- 
gaged in motion picture activities, and 
representatives of the lighting industry. 
The Committee's members are: 

H. R. Bell, Mole-Richardson Co. 

A. H. Brolly, Television Associates 

D. D. Cavelli, Signal Corps Photographic 
Center 

H. M. Gurin, National Broadcasting Co. 

H. A. Kliegl, Kliegl Bros. Universal 
Electric Stage Lighting Co., Inc. 

Ted Lawrence, Columbia Broadcasting 
Co. (Alternate) 

R. W. Morris, American Broadcasting 
Co. 

R. S. O'Brien, Columbia Broadcasting 
Co. 

Adrian TerLouw, Eastman Kodak Co. 

M. Waring, Allen B. DuMont Labora- 
tories 



Presented on May 3, 1951, at the Society's 
Convention in New York, by Richard 
Blount, General Electric Co., Nela Park, 
Cleveland 12, Ohio. 



R. L. Zahour, Westinghouse Electric 
Corp. 

In order to facilitate the investigation 
of lighting problems common to tele- 
vision stations, the membership has 
been divided into three groups. A 
Lighting Facilities Subcommittee in- 
cluding Mr. Brolly and Mr. Morris 
under the guidance of Mr. Kliegl are 
investigating: 

1. The problems involved in rigging 
lighting equipment. 

2. The power required. 

3. The methods of controlling and 
distributing power throughout the studio. 

In addition, this subcommittee plans 
to study the problems of electrical and 
lighting maintenance. 

This group works closely with a second 
subcommittee, that on Lighting Tech- 
niques, which was until recently under 
the direction of Mr. O'Brien. Mr. 
Gurin has agreed to take on the chair- 
manship of this group because Mr. 
O'Brien is now spending most of his 
time in Los Angeles. Messrs. Lawrence 
and Cavelli complete the group. They 
are engaged in a study of current lighting 
practice as applied to theaters, where 
staging techniques are determined to 
a large extent by the physical arrange- 
ments, to studios where a circus may 
follow a dramatic show, and to small 
fixed areas such as daily newscasts, 
culinary exhibitions, and childrens' pro- 
grams. While each area has some 
problems in common, each one must 
be handled separately if the maximum 



July 1951 Journal of the SMPTE Vol. 57 



69 



effect is to be obtained from the program. 
In addition this group has been asked 
to investigate special lighting effects 
that can be used to enhance the program. 
Some effects to be studied are back- 
ground projection, the use of follow 
spots, and pseudo sunlighting. 

A third very important group is 
engaged in the difficult activity of 
establishing a basic terminology. This 
group, including Messrs. Waring and 
TerLouw under Mr. Zahour's direction, 
has been very active in its efforts to 
establish names for various lighting 
techniques. This work is very necessary 
because even among the committee 
differences frequently arise over the 
meaning of various lighting terms. To 
date the committee has agreed to a divi- 
sion of lighting into three forms: 

1 . Base lighting, 

2. Accent lighting, and 

3. Effects lighting. 

Tentatively "base light" has been 
defined as uniform illumination required 
on a scene to produce a television image 



having satisfactory resolution, tonal 
gradation and signal-to-noise ratio at 
the point of origin. "Accent lighting" 
has tentatively been defined as a direc- 
tional illumination normally added to 
base lighting to improve the pictorial 
quality of the television image. No 
agreement has been reached on even a 
tentative definition of "effects lighting." 

The subcommittee is also investigating 
technique of light measurement. Realiz- 
ing that incident foot-candle measure- 
ments at times provide insufficient data, 
they are determining whether brightness 
measurements may also be used to 
advantage. 

The committee has been meeting at 
three-month intervals. Our membership 
is at present predominantly from the 
East and perhaps should be broadened. 
Mr. Bell is our sole representative on 
the West Coast and considering the 
television activities there other people 
may wish to contribute to this group. 
Their participation will be welcomed. 



70 



July 1951 Journal of the SMPTE Vol. 57 



Proposed American Standards 



ON THE FOLLOWING PAGES appear three 
Proposed American Standards pertaining 
to magnetic recording. They cover the di- 
rection of film travel, type of base, speed, 
dimension and positions of magnetic sound 
tracks on 35-mm, 17^-mm, 16-mm and 
8-mm motion picture films with standard 
perforations. 

The proposals are the result of the work 
of the Sound Committee's Subcommittee 
on Magnetic Recording, under the chair- 
manship of G. L. Dimmick. The sub- 
committee has been active since October 
1948, widely investigating the subject 
through meetings and correspondence 
among equipment manufacturers, studio 
sound departments and users of magnetic 
film. 

The Sound Committee and the Stand- 
ards Committee of the Society have ap- 
proved preliminary publication of the 
proposals in the JOURNAL for a ninety- 
day trial period. If, at the end of that 
time, no adverse criticism has been re- 
ceived, they will be processed as American 
Standards. 

In the case of the proposals for 35-mm 
and 17J^-mm film, one of the considera- 
tions affecting track location is the de- 
sirability of reproducing films of both 
widths on studio editing equipment in 
particular, and, consequently, the track 
location on 17^-mm film was made the 
same as the No. 1 track on 35-mm film, 
which is the track used when only one 
recording is made on 35-mm magnetic 
film. Careful cross-talk and scanning 
tests have shown the feasibility of recording 
three tracks on 35-mm film when it is 
desired to record dialogue, music and 
sound effects separately and simultane- 
ously, for example, for selective later use 
and resulting economy of film. 

The major equipment manufacturers 
are supplying equipment meeting these 
specifications which has proved satis- 
factory in motion picture studio opera- 
tions. It should be noted that the 35-mm 



and 17i^-mm proposed standards are for 
original recording and re-recording and 
do not apply to release film. 

The 16-mm proposal applies only to 
film having both picture and sound. 
Later committee work will cover 16-mm 
sound film with full-width magnetic 
coating. It should be noted that the 
photographic emulsion for picture is in 
the standard position for 16-mm films, 
and the magnetic coating is on the base 
side along the unperforated edge. The 
point of sound translation is also specified 
as 26 frames which is the same distance 
and in the same direction from the cor- 
responding picture as is the point of 
translation for photographic sound track. 
At least one projector manufacturer is 
presently considering manufacturing pro- 
jectors to this proposed standard and 
others are expected soon. 

The proposal for 8-mm film applies 
to film having both picture and sound. 
The magnetic coating is along the edge 
on the base side of the film outside the 
sprocket holes. The 24-frame speed is 
recommended for the more serious amateur 
and for use on professional sound films 
reduced from 35- or 16-mm material. 
The 18-frame speed has been selected to 
replace the former 16-frame standard 
because of the added improvement in 
sound quality and the somewhat smoother 
action in picture material. Several ex- 
perimental projectors have been built to 
support the practicability of the proposed 
standard. 

Subcommittee on Magnetic Recording 

G. L. Dimmick, Chairman 

Harold Bauman 

H. N. Fairbanks 

J. G. Frayne 

Robert Herr 

G. P. Mann 

M. G. Townsley 

D. R. White 



July 1951 Journal of the SMPTE Vol. 57 



71 



Proposed American Standard 

Dimensions for 

Magnetic Sound Tracks on 35 -Mm and 
Motion Picture Film 

(First Draft) 



PH22.86 



Note 1. This practice pertains to magnetic sound 
records, both single and multiple tracks, on 35-mm 
perforated film, and single tracks on 17!/2-mm per- 
forated film. 

Note 2. The film base shall be of the low-shrinkage 
safety type. 
Note 3. With the direction of travel as shown in 



the drawing, the magnetic material is coated on the 

upper side of the film base. 

Note 4. The magnetic coating is normally applied 

from edge to edge. 

Note 5. Track dimensions and positions are given 

in inches. All dimensions are given relative to un- 

shrunk film. 



RECORDING OR 
REPRODUCING 
HEADS IN LINE 






TRAVEL 



BASE DOWN 




0.150 



0.200,' 



0.002. 



0.150- 



-0.689 



0.004 



-35 MM 



ALL DIMENSIONS IN INCHES 



Note 6. Cutting and perforating dimensions and 
tolerances are identical to those given in Standard 
Z22.36, "Cutting and Perforating Dimensions for 
35-Mm Motion Picture Positive Raw Stock." 

7. Tfack #1 is the preferred position for 



35-mm single track recording, and is the standard 
position for l/Vi-mm recording. 

Note 8. Recording and reproducing speed shall be 
24 frames per second (Standard Z22.2). This is exactly 
96 perforations per second and approximately 18 
inches per second. 



NOT APPROVED 



72 



July 1951 Journal of the SMPTE Vol. 57 



Proposed American Standard 

Dimensions for 

Magnetic Sound Track on 16 - Mm 
Motion Picture Film 



PH22.87 



I! 

S9 



II 

t 



FRAME IN GATE 



LIGHT BEAM FOR 
DIRECT PROJECTION 
ON REFLECTING 
SCREEN 




ALL DIMENSIONS IN INCHES 



Note 1. The magnetic coating in the above draw- 
ing is on the side of the film toward the lamp on a 
projector arranged for direct projection on a reflec- 
tion-type screen. 



Note 2. Projection Speed 24 frames per second. 



NOT APPROVED 



July 1951 Journal of the SMPTE Vol. 57 



73 



Proposed American Standard 

Dimensions for 

Magnetic Sound Track on 8 - Mm 
Motion Picture Film 



PH22.88 



FRAME IN GATE 



LIGHT BEAM FOR 
DIRECT PROJECTION 
ON REFLECTING 
SCREEN 



U 




EDGE OF FILM 
AND COATING 



ALL DIMENSIONS IN INCHES 



Note 1. The magnetic coating in the above draw- 
ing is on the side of the film toward the lamp on a 
projector arranged for direct projection on a reflec- 
tion-type screen. 



Note 2. Projection Speeds 24 frames per second 
for professional use; 18 frames per second for ama- 
teur use. 



NOT APPROVED 



74 



July 1951 Journal of the SMPTE Vol. 57 



Board of Governors 



The third meeting of the Board of Gover- 
nors in 1951 was held in New York on July 
19. Half-year reports were presented on 
the state of the Society's finances, on recent 
membership promotion activities, on pub- 
lications and on the work of our engineering 
committees. Also, the Board approved 
the recommendations of the Nominating 
and the several award committees. 

FINANCIAL The financial aspects of 
all Society operations 
over the first six months and the resulting 
cash position were reported upon by F. E. 
Cahill, Treasurer, who presented his own 
report, and, in the absence of R. B. Aus- 
trian, also presented the Financial Report. 

With the exception of two membership 
activities, business operations for the first 
six months of 1951 were about even with 
the first half of the annual budget adopted 
in January and well ahead of last year. If 
the present trend continues, and presum- 
ably it will, this should be the best financial 
year in Society history. But the Board 
was in agreement that even though the 
monthly and quarterly operating state- 
ments show an attractive picture at the 
moment, the officers and Headquarters 
staff members responsible for budgets and 
financial plans should not relax their atten- 
tion. They must not assume that "busi- 
ness as usual" represented by last year's or 
this year's financial reports is an automatic 
and perpetual condition. With the Society 
now 35 years old and in every respect 
healthy enough to continue for another 
long lap, it would be wise to base plans for 
the future on a period somewhat longer 
than just "next year." 

A program of long range financing will 
be prepared for consideration by the Board 
at its October meeting. Along with the 
obvious provisions for sustained high level 
income over a period of several years, 
there should be plans for continued expan- 
sion of the work of engineering committees, 
the Journal and other services to the mem- 
bers and to the industries that employ them. 

MEMBERSHIP Each year the Society 
gains new members 

but for some time the number of applicants 
accepted over a 12-month period has very 
nearly been offset by the number of current 
members who are delinquent in payment of 



their dues. Although the net figure, that 
is, the total of all members in all grades, has 
always been higher at the end than at the 
beginning of each calendar year, the growth 
rate from year to year has been disappoint- 
ing. To partly remedy the situation the 
Board six months ago authorized employ- 
ment of a full time Membership Secretary. 
Mrs. Beatrice Gonlon of the staff began 
work in that capacity in March and a re- 
port of her efforts over the 4-month period 
was presented. Guests who had attended 
the 69th Convention were sent membership 
invitations and out of 25 replies received by 
July first, 16 applications were approved. 
Letters addressed to those current members 
who had not sent in their dues for 1951 pro- 
duced a 10% return, or about 40 reinstate- 
ments. Other specific efforts accounted 
for a reasonable share of the 334 new mem- 
bers who joined before July 1. The Board 
called for increased effort on the part of all 
members of the Membership and Sub- 
scription Committee and urged that the 
major share of this effort be directed toward 
the up and coming young engineers who 
could derive real benefit from the Journal 
and other Society activities. They would 
also doubtless continue as members for a 
long time to come, if the Society is actually 
serving its fundamental purpose. 

PUBLICATIONS Editorial Vice Presi- 
dents C. R. Keith 

and J. G. Frayne, the Editor Vic Allen, 
and Arthur Downes, Chairman of the 
Board of Editors, have devoted a great deal 
of effort to tightening the editorial policy of 
the Journal. They aimed at reducing de- 
lays between presentation and publication 
of technical articles, raising the average 
levels of both editorial and technical quality 
of papers submitted for the Journal so there 
would be a wider selection of suitable ma- 
terial from which to assemble any given 
issue and to increase the amount of infor- 
mation published. In addition, they 
wanted more pages in the "back of the 
book," this section that reports on the 
Society and its internal workings. 

In a written report submitted by John 
Frayne, who was not able to attend, ample 
evidence of progress was presented. The 
change to two column format authorized 
last October had been made on schedule, 
beginning with the issue for January. New 



75 



paper and ink were also adopted. These 
changes were intended to give more words 
per page, improve appearance and read- 
ability, and at the same time permit some- 
what greater flexibility in make-up of the 
"back of the book" and in articles with 
numerous illustrations. Twenty-five per 
cent more material was contained in the 
first six issues for 1951 than appeared in the 
first six last year and 60 per cent more 
than in the same period in 1 947. 

By working closely with the Mack Print- 
ing Company and by applying added per- 
sonal effort, Vic Allen was able to make the 
Journal a larger, more professional maga- 
zine. In recent months, however, the 
addition of such items as the High-Speed 
Photography Bibliography, the 5-Year 
Index, the new style volume title page and 
index that appeared in June plus a series of 
technical papers that required more de- 
tailed care to publish, required so much 
extra attention that publication dates be- 
gan to lag. Extra manpower seemed to be 
the only solution, so on Dr. Frayne's 
recommendation the Board authorized Vic 
Allen to employ an Assistant Editor, in- 
creasing the editorial staff to three. 

The Papers Committee, for which the 
Editorial Vice-President is responsible, has 
been working seriously on plans for the 
70th Convention. Fred Albin, Vice-Chair- 
man, and Ed Seeley, Chairman, have 
switched the program into high gear. 

Development of a high quality public 
address and discussion recording system for 
use at conventions had been assigned to 
Dr. Frayne. He appointed a committee 
under the chairmanship of Harry Braun to 
work out the detailed design. The Com- 
mittee's recommendations were approved, 
so that work can be started at once. 

ENGINEERING Fred T. Bowditch, 
Engineering Vice- 

President, reviewed the system of Stenotype 
recording and transcription used in the 
preparation of minutes of many of the 
engineering committees' meetings held 
during the 69th Convention. He criti- 
cized the use of "outside" help on this job 
because the results did not justify the ex- 
pense. For that reason future meetings of 
engineering committees that Hank Kogel, 
Staff Engineer, cannot attend will be re- 
ported by a recording secretary, whom the 
chairman will appoint on the spot. 



One of the methods of measuring lens 
transmission that the Optics Committee 
had considered suitable for a proposed 
standard is the subject of a U. S. Patent 
assigned to the Radio Corporation of 
America. Mr. Bowditch reported that 
since the patent could have been a serious 
obstacle to general use of the method it was 
fortunate that the Radio Corporation of 
America had seen fit to offer a paid up 
license to anyone interested for the sum of 
$10.00. Appreciation had been formally 
expressed in the June Journal. 

Most important engineering item on the 
Agenda was concerned with the position 
which the Society would assume in connec- 
tion with the forthcoming hearings on 
Theater Television of the Federal Com r 
munications Commission. 

After duly considering the combined 
views of the Theater Television Committee 
and its Subcommittee on Distribution 
Facilities, under G. L. Beers and Pierre 
Mertz, Chairmen, the Board agreed that 
the Society should act on the recommenda- 
tions and not make an appearance. Steps 
taken to notify FCC, industry trade groups 
that took part in this work and the press are 
reported upon elsewhere in this issue. 

CONVENTIONS Although most mem- 
bers who help put on 

Society Conventions twice each year are 
concerned with only one at a time, Con- 
vention Vice-President Bill Kunzmann is 
always looking far into the future. Con- 
vention hotels are booking large conven- 
tions as far as two to three years ahead, so 
Bill has tied up these dates : 

70th Convention, Hollywood Roosevelt, 
Hollywood, Calif., October 15-19, 
1951 

71st Convention, Hotel Drake, Chicago, 
111., April 21-25, 1952 

72nd Convention, Hotel Statler, Washing- 
ton, D.C., October 5-10, 1952 

73rd Convention, Hotel Statler, Los 
Angeles, Calif., April 26-30, 1953 

74th Convention, Hotel Statler, New York, 
October 4-9, 1953 

The Board of Governors authorized these 
five reservations and learned that all Com- 
mittees for the 70th Convention have been 
appointed and are now hard at work. De- 
tails are given elsewhere in this issue. 



76 



70th Semiannual Convention 



Hollywood Roosevelt Hotel, Hollywood, Calif., October 15-19, 1951 



You can bet that the 70th Convention 
will be up to Bill Kunzmann's usual stand- 
ards. He has turned in two good ones 
every twelve months for 35 years and as 
Convention Vice-President and entre- 
preneur par excellence he should make the 
next the best so far. 

During June, Bill met twice with Presi- 
dent Peter Mole and the Pacific Coast Sec- 
tion Managers to arrange the feature 
events. He has prepared a list of these 
items in sequence and as soon as essential 
details are filled in by his planning team 
Bill will arrange for Vic Allen to print the 
advance notice and mail it to all members. 
The customary hotel reservation card will, 
of course, be included as will session titles 
and enough general information about the 
program to enable members to crystallize 
their personal plans. 

Following the advance notice (by the 
shortest possible time interval) will be the 
tentative program, also to be printed by 
Vic Allen and mailed to all members. 
For each paper listed the tentative program 
will show title, author, author's affiliation, 
and a brief abstract of the paper's contents. 
Although some changes are inevitably 
made in the separate items and in their 
order of presentation after the tentative 
program is completed and before the final 
program goes to press, every effort is made 
to keep these changes to a minimum. The 
final program will be distributed at the 
Registration Desk on opening day, Mon- 
day, October 15. 

PROGRAM Fred Albin, American 
Broadcasting Co., 4151 
Prospect Ave., Holly- 
wood, Calif. 

As Papers Committee Vice-Chairman for 
the Hollywood area, Fred is in charge of 
organizing technical sessions, perhaps in- 
cluding a symposium or two. In making 
up the Program, he will be able to draw 
from fifty or sixty separate contributions 
offered directly by individuals or secured 
by other members of the Papers Committee. 
Help with procedure, and in the way of 
program suggestions, will come from J. G. 
Frayne, Editorial Vice-President, and E. S. 



Seeley, Chairman of the Papers Com- 
mittee. When enough manuscripts have 
been received to give form to the program 
schedule, Fred will draft the tentative 
program. He urges that prospective 
authors who have not furnished either 
manuscript or author's form do so at once. 
Proper blanks are available from any of 
the Vice-Chairmen whose names are listed 
on p. 690 of the June Journal. 

LUNCHEON AND BANQUET 

Norwood Simmons, Eastman Kodak Co., 
6706 Santa Monica Blvd., Hollywood 
38, Calif. 

An essential assignment in connection with 
the Monday luncheon and Wednesday 
banquet has been given to Norwood. He 
will schedule the presentation of all annual 
awards and help select the luncheon 
speaker. As Peter Mole's aide he will sec 
that the "official" parts of both social 
events begin and end on time. He will 
also receive official guests, seat them, and 
serve as assistant host for each occasion. 

LADIES Mrs. C. R. Daily, 113 N. 
Laurel Ave., Los Angeles 36. 
As Chairman of the Ladies Committee Mrs. 
Daily will be official Convention Hostess. 
She will appoint the Ladies Committee, 
help with the program of entertainment 
for those of the fairer sex who attend, and 
while the Convention is in session she will 
be their guide and mentor. 

MOTION PICTURES 

Sid Solow, Consolidated Film Indus- 
tries, 959 Seward St., Hollywood 38. 
Motion Picture short subjects of better 
than average quality are used to open all 
technical sessions. Sid will schedule and 
book all the required films, arrange for de- 
livery to the Hollywood Roosevelt before 
each session, and for pick-up afterward. 
In addition (as is customary) he will be 
superintendent of nonsense and engage the 
entertainer for the Monday luncheon. 

PUBLICITY Harold Desfor, RCA Vic- 
tor Div/, Camden, N.J. 
Taking a ten-day leave of absence from his 
regular job, Harold will set up publicity 



77 



headquarters just outside the Manager's 
office in the Hollywood Roosevelt Hotel. 
Beginning Monday he will prepare one or 
two daily press releases telling the story of 
the Convention as it unfolds. Before the 
doors open, however, he will have ex- 
amined all manuscripts for newsworthiness 
and have prepared written abstracts (in 
layman's language) of the important parts 
of each paper. Reporters from trade and 
city papers can then study them all in 
understandable capsule form. 



PRICES Bill Kunzmann, National Car- 
bon Division, Box 6087, 
Cleveland 1, Ohio 

Registration for the week $ 5 . 00 

Registration for a single day 1 . 00 

Ladies Registration (week) 2 . 00 

Luncheon (tax and tip included) . 4 . 00 
Banquet* (tax, tip and cocktails 

included) 11.00 

* Bill Kunzmann said to remind everybody 
that the banquet is informal. 



Theater Television and the FCC 



THE ENTIRE FIELD of theater television 
reached and passed an important milestone 
in the month of July 1951. After pleading 
the cause of theater television in many 
places and with great enthusiasm over the 
better part of a decade, the Society is no 
longer the only vocal public proponent. 
Theater circuits, exhibitors' trade organi- 
zations, manufacturers and the common 
carriers have joined the parade. 

Equipment is being made, sold, installed 
and used on a commercial scale and the 
companies concerned with all aspects of 
equipment, operation and programming, 
as well as their trade organizations are be- 
ginning to move in a single general direc- 
tion. Before long this link of communica- 
tions between motion picture exhibition 
and television will be an integral part of 
the nation's entertainment industry. 

As a consequence of this imminent matu- 
rity, our Theater Television Committee and 
its Subcommittee on Distribution Facilities 
believe that the new industry is well able to 
solve its own commercial problems. They 
have so advised the Board of Governors, 
recommending that the Society make no 
further appearance before the Federal 
Communications Commission in this con- 
nection, on its own initiative. Forthcom- 
ing hearings of the FCC described in 
Docket No. 9552 fall into the "commercial 
problems" category, because in addition to 
considering certain technical matters, the 
hearings will produce specific requests for 
allocation of sections of the radio frequency 
spectrum to the use of theater television. 
And they will also produce requests for the 
assignment of particular channels within 
those "theater television bands," to par- 



ticular commercial interests. Using these 
two factors as a basis for its decision, the 
Board of Governors at its meeting in New 
York on July 19 ruled that the SMPTE 
would not appear at the forthcoming hear- 
ings. 

FCC 

Immediately following the Board Meet- 
ing, President Mole addressed the following 
letter to Mr. T. J. Slowie, Secretary of the 
Commission : 

"The Society of Motion Picture and 
Television Engineers has given consider- 
ation to having its representatives appear 
at the hearings of the Federal Communica- 
tions Commission beginning the first week 
in December and relating to channel 
assignments and related matters for theater 
television. The Society has for many years 
been active in studies of theater television 
methods, equipment and engineering as- 
pects. 

"Its primary functions in the develop- 
mental stages of theater television include 
the following: to coordinate the varied 
approaches which individuals and com- 
panies in the motion picture industry have 
taken toward the problems of creating the 
means of theater television; to establish 
desirable performance objectives practical 
of attainment at each stage of the art, and 
economic in the sense that equipment and 
facilities must be both manufacturable and 
operable; to arrange for the free exchange 
of information on video bandwidth, number 
of lines and suitable signal-to-noise ratios. 
These results have been accomplished 
through the Society's engineering com- 
mittees. 



78 



"The consequence of this SMPTE co- 
ordination will doubtless be constructively 
evident in the statements soon to be filed 
with the Commission by commercial in- 
terests who propose to establish and to 
operate portions of a national theater tele- 
vision service. To further the develop- 
ment of such a service the Society is ready to 
serve the Commission as well as the motion 
picture industry through its study of par- 
ticular technical questions. 

"The Board of Governors of the Society 
believes that the Society's mission in the 
present preliminary stage of theater tele- 
vision development has been accomplished, 
citing as evidence the present broad interest 
of the industry as well as the constructive 
measures which the industry now proposes. 
Since the Society is a technical organization 
(and not a commercial institution), and 
since it will, of course, not propose to oper- 
ate any portion of the theater television 
service, it does not propose to apply for the 
use of a band of frequencies in the radio 
spectrum, and for that reason does not pro- 
pose to file an appearance nor otherwise 
participate in the forthcoming hearings. 
Further, the Society is convinced that the 
matters under consideration at these hear- 
ings can be adequately and informatively 
handled by the qualified engineering repre- 
sentatives of motion picture organizations 
there appearing. 

"The Society has historically taken a 
constructive, cooperative and active posi- 
tion with respect to theater television. It 
is a pleasure to report that its Board of 
Governors continues its full interest in that 
field and has today authorized the following 
statement of its position with respect to the 
forthcoming hearings in the matter of 
Allocation of Frequencies and the Promul- 
gation of Rules and Regulations for a 
theater television service. 

1. The SMPTE, as a scientific and 
engineering society, is concerned pri- 
marily with technical matters. It is not 
concerned with commercial or industrial 
matters as such, and does not undertake 
to represent or speak for the motion pic- 
ture industry or its parts. 

2. The field of theater television has 
now reached a stage of technical and 
commercial development such that indi- 
vidual organizations appear qualified to 
express their viewpoints. Accordingly, 
the participation of the SMPTE in 



regulatory hearings no longer appears 
necessary. 

3. However, upon the request of the 
FCC the SMPTE will assign to its tech- 
nical committees the task of studying 
specific technical questions and will 
thereafter present to the Commission the 
technical opinions and data they can 
produce. 

"The Society particularly directs the 
attention of the Commission to its willing 
offer of further technical service whenever 
requested." 

Industry 

Since other industry groups had of recent 
years been either taking an active part in 
the Society's committee deliberations or 
following closely, developments within its 
committees, it was particularly important 
that they know where the Society stands at 
the present time. To keep them informed, 
President Mole wrote on the morning of 
July 20 to the Presidents or senior staff 
members of these eight organizations : 

Motion Picture Association 

Theatre Owners of America 

Society of Independent Motion Picture Pro- 
ducers 

Allied States Association of Motion Picture 
Exhibitors 

Motion Picture Research Council 

Metropolitan Motion Picture Theatre 
Owners Association 

Independent Theatre Owners Association 

National Exhibitors Theater Television 
Committee 

Enclosing a copy of the statement to the 
FCC, the letters read in part : 

"We believe the cooperative spirit that 
has characterized the industry-wide interest 
in theater television over the last few years 
has formed a firm basis for an effective 
theater television service, and we earnestly 
hope it will continue. The present outlook 
is most encouraging. 

"In the same constructive spirit I have 
been asked by our Theater Television 
Committee and its Subcommittee on Dis- 
tribution Facilities to extend the following 
invitation to all industry groups who have 
taken part in our work or otherwise shown a 
serious interest. If you find it convenient 
please pass this invitation along to the 
members of the [your organization] as 



79 



evidence that the SMPTE has no intention 
of stepping aside at this juncture. 

" [Your organization] is invited to call 
upon the Society of Motion Picture and 
Television Engineers at any time for 
assistance in the study of specific technical 
matters. The results of such studies 
would, as is customary, be presented for 
free use of the industry at large." 

Continued Interest 

Mr. Mole and the Board felt it was im- 
portant to avoid giving the impression that 
the Society was stepping aside now, after so 
many years of active interest in promoting 
early technical progress in this compara- 
tively new field. The present move im- 
plies rather that the Theater Television 
Committee is now ready to concentrate on 
technical details and, like all other engi- 
neering committees within the Society, is at 
the service of all segments of the industry. 

For a review of past work in this connec- 
tion, look up the following : 

1. "Statement on theater television," Thea- 
ter Television Committee, D. E. Hynd- 



man, Chairman, Jour. SMPE, vol. 53, 
pp. 354-362, Oct. 1949. 

2. "FCC allocation of frequencies for thea- 
ter television," Jour. SMPE, vol. 53, pp. 
351-353, Oct. 1949. 

3. "Theater television," Theater Tele- 
vision Committee, D. E. Hyndman, 
Chairman, Jour. SMPE, vol. 52, pp. 
243-272, Mar. 1949. 

4. "Statement of SMPE on revised fre- 
quency allocations," Paul J. Larsen, 
Jour. SMPE, vol. 48, pp. 183-202, Mar. 
1947. 

5. "Report of the Committee on Television 
Projection Practice," P. J. Larsen, 
Chairman, Jour. SMPE, vol. 47, pp. 
11 8-1 19, July 1946. 

6. "Frequency allocations for theater tele- 
vision," Jour. SMPE, vol. 45, pp. 16-19, 
July 1945. 

7. "Statements of the Society of Motion 
Picture Engineers on allocation of fre- 
quencies in the radio spectrum for thea- 
ter television service as presented before 
the Federal Communications Com- 
mission," Jour. SMPE, vol. 44, Feb. and 
April. 1945. 



Letters to the Editor 



Re: A. Study of Current Misconceptions in the Optical Theory of 
Rotating Prisms for High-Speed Cameras 



Summary: The analysis of the rotating prism, 
as published by J. H. Waddell in this 
JOURNAL, is wholly invalidated by an initial 
mathematical error. The correct calculation 
shows increasing speed of image displacement 
for increasing angle of rotation a result directly 
opposite to that obtained by Waddell. More- 
over, the advertised statement that "high index 
low dispersion glass" improves the resolution is 
without real foundation, as the influence of the 
value of the refractive index on the prismatic 
aberrations is practically insignificant. 

A DESCRIPTION of the image forma- 
tion by rotating prisms was given by J. H. 
Waddell, 1 with particular attention to the 
change in the speed of image displacement 
with increasing angle of rotation. 

Unfortunately, a substantial mathe- 
matical error crept into the basic formula 
upon which WaddelPs investigation was 
built up. His formula (5), which should 



be the differential quotient of equation (4), 
is essentially incorrect. The mistake in 
differentiation led to the conspicuously 
false Fig. 2 in Waddell's paper, showing a 
curve turning downward to zero speed for 
increasing angle. In reality, the correct 
curve turns upward with increasing angle. 
The writer has previously given a quan- 
titative survey of the optical aberrations in 
question. 2 The image produced by the 
camera lens is continuously displaced by 
the rotating prism during the exposure. 
The displacement is 



(D 



in which D is the thickness of the polygonal 
prism, n is the refractive index, and x is the 
angle of rotation in radians (i.e., the angle 
between the optical axis and the normal to 
the prism face). 



80 



The angle x being proportional to the 
time, the speed of the image displacement 
is proportional to the differential quotient 
of formula (1): 



D 



n - \ 



This shows a fast increase of the image dis- 
placement for greater values of the angle x. 
Against this result, Waddell's Fig. 2 shows a 
decrease to zero and even to negative speeds 
with increasing angle, which is obviously 
wrong. 

In Waddell's paper, as well as in other 
descriptions, particular emphasis is laid on 
the statement that improved resolution has 
been achieved by a new prism made of 
"high index low dispersion glass." How- 
ever, this cannot be motivated by the slight 
influence of the refractive index on the 
nonlinear term in formula (1), as the whole 
effect of this aberration is practically oblit- 
erated by a suitably chosen value for the 
thickness D of the prism, which fact should 
be carefully realized. The value of the 
thickness D is usually chosen so that formula 
(1) indicates complete image coincidence 
for three positions of the rotating prism, 
representing, the beginning, the middle 
and the end of the exposure time. Thus 
any possible effect of nonlinearity is de- 
liberately restricted to some intermediate 
positions of the prism, which means such 
small numerical values for the residual 
nonlinearity, that this aberration is prac- 
tically eliminated, irrespectively of the 
value of the refractive index. It would be 
rather meaningless to argue that the 
coefficient of x 3 in formula (1) has the value 

for n = 1.5, and the smaller value for 
18 24 

n = 2.0, since the practical effect on the 
image formation in either case is negligible, 
if the exact value for the thickness of the 
prism has been properly chosen. 

As far as dispersion is concerned, its 
effect is proportional to the angle of rota- 
tion during the actual exposure in the high- 
speed camera, but it remains negligible for 
any rotating prism of low dispersion glass. 
Thus it remains to find out how other rota- 
tional aberrations depend upon the refrac- 
tive index. In this respect, only prismatic 
coma and astigmatism have to be consid- 
ered. The numerical value of these aber- 



rations is proportional to , if n is again 

the refractive index of the prism. Conse- 
quently, under otherwise identical condi- 
tions, a polygonal prism of high index glass 
(e.g. n = 1.8) would reduce prismatic coma 
and astigmatism by only 20%, as compared 
with the case of a prism of low index glass, 
such as n = 1.5. The practical insignifi- 
cance of such a slight change in the size of 
aberrations can be illustrated as follows: 
Let us consider a camera with a rotating 
prism of high index glass (n = 1.8), under 
the condition of an overall limitation of the 
angle of incidence to 7-g- . Replacing this 
high index prism by a low index (n = 1.5) 
prism of suitable thickness, the optical 
aberrations remain exactly the same if the 
maximum angles of incidence are limited 
to 7, i.e., only half a degree below the 
limits referred to in the allegedly ideal case 
of a high index glass. 

This comparison shows that there is no 
real meaning in the argument of the "high 
index low dispersion glass," however eso- 
teric an appeal might emanate from it. 

The problem of optical improvement of 
this type of high-speed cameras is neither 
so simple nor so limited and hopeless, as 
suggested by recent literature. As soon as 
priority is granted to the optical problem, 
an unexpected progress in the construction 
of high-speed cameras of the rotating prism 
type will become possible. The presently 
prevailing attitude is based on the principle 
of a preconceived gear-box, which is really a 
Procrustean bed into which the optics has 
to be stretched or mutilated. There are 
surely more drawbacks than advantages in 
having a gearing between film driving and 
prism movement. But such a gearing is 
not an inherent feature of the construction, 
as the optical solution is compatible with a 
single rotating unit, serving the double pur- 
pose of optically displacing the image and 
mechanically displacing the film. 

March 24, 1951 J. KUDAR 

601 W. 113th St. 

(Apt. 10F) 

New York 25, N.Y. 

References 

1. J. H. Waddell, "Design of rotating prisms for 
high-speed cameras," Jour. SMPE, vol. 53, pp. 
496-501, Nov. 1949. 

2. J. Kudar, "Optical problems of the image forma- 
tion in high-speed motion picture cameras," Jour. 
SMPE, vol. 47, pp. 400-403, Nov. 1946. 

81 



Errata 



J. H. Waddell, "Design of rotating prisms for high-speed cameras, Jour. SMPE, vol. 53. 
pp. 496-501, Nov. 1949. 

(ss 1 } _ , _ fcos i 4(n 2 sin 2 i) cos 2i sin 2 2i~\ 
dt 4(n? sin 2 z) 



PP 
Page 497 : For 



read 



d(ss'} 



4(n 2 sin 2 i) cos 2i sin 2 2i 



4(n* - sin 2 i) 
Page 498: For Fig. 2, substitute the figure shown on p. 83. 



(5) 

(5) 



Reply to the Letter Above 

In reviewing the Letter to the Editor 
by Mr. Kudar, in reference to a study of 
current misconceptions in the optical 
theory of rotating prisms for high-speed 
cameras, there are a number of very inter- 
esting observations to be made in reference 
to this critique by Mr. Kudar. 

There was, as has been turned over to 
the Society, a typographical error in 
Formula 5 in the paper, Design of Rotating 
Prisms for High Speed Cameras by John H. 
Waddell, and consequently in the calcula- 
tions that illustrated Fig. 2 positive values 
are shown rather than negative values as 
the relative velocity. However, quoting 
from a letter from one of my former asso- 
ciates, it is to be pointed out that this does 
not affect the validity of thinking in the 
design of rotating prisms in the least. 

As one recalls from the oral presentation 
of this paper in the city of Washington at 
the first High-Speed Photography Sym- 
posium, the data to indicate that the high 
index glass prisms would prove of ad- 
vantage was illustrated with a number of 
curves covering the various types of pris- 
matic aberrations and distortions from the 
Kudar paper which was published in the 
Journal (vol. 47, pp. 400-403, Nov. 1946). 
In those figures it can be shown conclu- 
sively, as was demonstrated, that the opti- 
cal quality of the image is improved by 
going to the higher index glass. Further- 
more with the new Kodak high index low 
dispersion glass many improvements have 
been made practically in the formation of 
the optical image transmitted through the 
prism and on to the film plane both by the 
use of this glass and reducing the angle of 
incidence through which the exposure was 
made. 

Practical considerations in the design of 



high-speed cameras indicate that the 
engineers are more interested in a very 
short cycle of exposure than such as would 
be required for continuous projection. 

There is considerable stress placed by 
Mr. Kudar in the selection of the high in- 
dex glass versus the low index glass. It 
must be remembered that radius in centrif- 
ugal force is reduced through the use of 
high index glass and any factor which can 
be made to reduce centrifugal force in very 
high speed moving mechanisms is to be 
considered seriously. It is not felt that 
the approach has been esoteric as Mr. 
Kudar has emphasized but primarily from 
a practical design wherein the practical 
optics do not necessarily meet with the 
approval of the theoretical man. There 
has to be a compromise between theory and 
practice at all times and when one is able 
to design a camera which produces a pic- 
ture which is as steady as one taken with an 
intermittent camera and with resolving 
power equal to that of the normally fast 
films of today the compromise in the prac- 
tical optics has been well satisfied. 

As far as the comment about gear trains 
et cetera, they do not enter into the picture 
in the least because the tolerances to which 
cameras are made now are primarily pro- 
prietary information and therefore it is not 
felt that it is wise to discuss tolerances of 
manufacture of high-speed motion picture 
cameras in a paper of this type. 

It is felt that if one examines pictures 
taken with the rotating prism cameras of 
today that they will be very satisfied with 
the photographic quality obtained. True, 
the next problems of design, of course, are 
to produce sprockets and other parts of the 
moving mechanism which are more 
ideally suited for both super speed opera- 
tion wherein the cameras will operate at 



82 



dt 



c-t 



r *; TH/CKNESS OP 

rrv. - INDEX 
-A- -! ANGLE OF 

I--- ANGULAR VELOCITY OF 

*-* VELOCITY OF /AGE ;01SR.AGMNT 






o 
o 



UJ 



I 






1.2 



1,0 



RATIO 

1$ 1.0 



;-fO 



IS 1024 '; AT 






ANGLE OF 



four times their present rate of speed or 
larger image size such as could be obtained 
on a full frame 35-mm camera both of 
which are under current development. 



[At press time, a Letter from Dr. Kudar 
came to the Editor further setting forth Dr. 
Kudar's ideas on the problem of centrifugal stress 
and strain in rotating prisms. ] 



June 20, 1951 



JOHN H. WADDELL 
850 Hudson Avenue 
Rochester 21, N.Y. 



83 



Engineering Activities 



ASA Standards for Color 
American Standard Methods of Measuring 
and Specifying Color, Z58.7.1-3, 1951, 
approved April 13, 1951, have been pub- 
lished by the American Standards Associ- 
ation. They consist of three parts, each 
one numbered differently so that workers 
concerned with separate phases may refer 
to each part separately. This Z58.7 set of 
standards is a revision of War Standard 
Z44-1942, taken over for revision by the 
recently formed ASA committee Z58, 
Sectional Committee on Standardization 
of Optics, Francis W. Sears, Chairman, 
sponsored by the Optical Society of Amer- 
ica. The revision was handled by a sub- 
committee of which David L. MacAdam 
of the Eastman Kodak Co. served as chair- 
man. The three standards are titled as 
follows : 

Z58.7.1-1951, American Standard Method 
of Spectrophotometric Measurement for 
Color; 

Z58.7.2-1951, American Standard Method 
for Determination of Color Specifica- 
tions ; 

Z58.7.3-1951, American Standard Alterna- 
tive Methods for Expressing Color 
Specifications. 

The first standard states the scope, then 
sets up seven provisions that relate to 
Spectrophotometric measurement of color: 
1, wavelength range; 2, bandwidth; 3, 
stray radiant energy; 4, nominal wave- 
length; 5, photometric scale; 6, spectral 
reflectance; 7, spectral transmittance. 
This is followed by a discussion, with nine 
numbered paragraphs. 

The second standard sets up procedures 
for computing color specifications from 
Spectrophotometric measurements in terms 
of the well-known and widely used tri- 
stimulus values X, Y and Z which are 
based on values for the equal-energy spec- 
trum (and the "Standard Observer") 
adopted in 1931 by the International Com- 
mission on Illumination (380-780 m/*). 
Tables of values I.C.I. Standard Source C 
(380-770 m/ti) are included for use both by 
the weighted ordinate (10-rmx interval) 
method and the selected ordinate method 
of calculation. Trichromatic coordinates 
(x, y, z) are given for the spectrum (380 to 



780 m/i in 5-mjLt intervals). The usual I CI 
(x,y)-chromaticity diagram is presented as 
the American Standard Chromaticity 
Diagram. All illuminations other than 
ICI Standard Source C are referred to as 
"nonstandard," and while it is pointed out 
that sometimes it may be important to use 
other sources in computation, the result 
"should not, however, be designated 
American Standard." 

The third standard establishes alterna- 
tive methods for expressing color in terms 
of dominant wavelength, purity and 
luminance; and secondly, in terms of 
Munsell hue, Munsell chroma and Munsell 
"value," "by interpolation in tables and 
charts prepared by the Subcommittee on 
the Spacing of the Munsell Colors of the 
Colorimetry Committee of the Optical 
Society of America, 1943." It is noted 
that these two sets of terms specify quanti- 
ties that correlate more or less satisfactorily 
with hue, saturation (chroma) and light- 
ness (value), defined as "features of color 
sensation and perception," but that the 
Munsell terms correlate somewhat better 
than dominant wavelength, purity and 
luminance for opaque, reflecting materials 
under usual conditions of observation. 

There are many things in these standards 
that need to be studied. In some respects 
they are wordy and less clear than Z44- 
1942 which they are intended to replace. 
In other respects they are an improvement. 
The limitation they set, * that to comply 
with American Standard Methods one 
must do all colorimetric measurement and 
specification through spectrophotometry, 
is so extreme and so impracticable, in the 
opinion of the reviewer, that it will cer- 
tainly lead to revisions in the standards if 
they are to become as useful in American 
practice as they could be. Omission of 



* The standards set this limitation, 
although the Foreword states that any 
method may be used for sections 1 and 2 
that will provide equivalent results. Spe- 
cific note is made, however, that "This 
Foreword is not a part of the American 
Standard Methods . . . . " Either the note 
is incorrect, so that the Foreword should be 
a part of the standard, or only specifica- 
tions arrived at through spectrophotometry 
comply with the standard methods. 



84 



direct and full reference to the inter- 
nationally adopted resolutions of the 1931 
(and other) meetings of the International 
Commission on Illumination, as the basis 
for these American Standards, is an omis- 
sion that is confusing. American accept- 
ance of so much of the IGI recommenda- 
tions for colorimetric practice is so very 
general that it would have clarified the 
meaning of some of the American Stand- 
ards provisions if more direct reference 
were made as to those parts adopted, and 
those parts omitted, of the IGI recommen- 
dations. (A typographical error in the 
heading of the last section of the third 
standard should be noted: "Deflecting" 
is written for Reflecting.) 

However, the committee has worked 
long and hard to reach a point of agree- 
ment and of ASA approval and publica- 
tion. Dr. Mac Ad am served as chairman 
of the subcommittee, and he had on the 
committee many members who served as 
representatives of ASA member-associ- 
ations, firms, or cooperating governmental 
organizations. Among them were: Carl 



Z. Draves (for the AATCC) ; I. H. God- 
love (for the Ansco division of General 
Aniline and Film Corp.); S. M Newhall 
(for APA); M. Rea Paul (for ASTM); 
A. J. Werner (alternate for Corning Glass 
Works); Wm. F. Little (for Electrical 
Testing Laboratories) ; Norman F. Barnes 
(alt. for General Electric Co.); C. L. 
Crouch (alt. for IES); W. R. Erode (for 
OSA); Fred E. Altman (for SMPTE) ; 
D. B. Judd (for National Bureau of Stand- 
ards) ; and E. K. Kaprilian (for Dept. of 
Army Signal Corps). (Initials have been 
used for ISGC member-bodies.) 

Later it may be useful to publish a critical 
review ol' these standards, but at present it 
seems enough to let all color workers know 
that we now have available a set of ASA 
standards for use in measuring and specify- 
ing color. Copies of the set of three 
standards (15 pp.) may be purchased at 
fifty cents per set direct from the American 
Standards Association, 70 E. 45th St., 
New York 17. D.N. (Reprinted from I-SCC 
News Letter No. 94) 



Back Issues of the Journal Available 

Three and one-half years of the Journal, July 1947 through December 1950, are avail- 
able at the job lot price of $25.00 from Mr. Max Prilik, c/o Circle Theater, 82 H Grant 
Circle, The Bronx 60, N.Y. 



SMPTE Officers and Committees: The roster of Society Officers and the 
Committee Chairmen and Members were Published in the April Journal. 



Obituary 



Albert L. Raven died on July 11 after a 
long illness at the age of 75. He was 
President of the Raven Screen Corp., 124 
E. 124th St., New York, which he founded 
in 1921. 

As a young man he had traveled on cruise 
ships as a photographer for Underwood & 
Underwood. He also had been employed 
by the Nicholas Power Co., working with 
motion picture equipment, before develop- 
ing and marketing his ideas for motion pic- 
ture screens. He invented a perforated 
screen and perfected a "halftone" screen 



with high reflective powers accomplished 
with a facing of cotton backed by titanium 
and rubber to get white color and opaque- 
ness. This screen was used by Eastman 
Kodak Co. for its Cavalcade of Color at the 
New York World's Fair. In the 1930's 
the Raven Screen Co. boasted "a screen in 
every house on Broadway." More re- 
cently the company has concentrated on 
screens and related equipment for homes 
and institutions. Mr. Raven had been a 
member of this Society since 1924. 

85 



New Members 



The following members have been added to the Society's rolls since those published last 
month. The designations of grades are the same as those used in the 1950 MEMBERSHIP 
DIRECTORY. 



Honorary (H) Fellow (F) Active (M) 

Aerts, Rene, General Sales Manager, The 
Gevaert Co. of America, Inc., 423 W. 
55 St., New York 19, N.Y. (A) 

Applebaum, Joseph H., Cameraman, 
Coronet-Industrial Newsreels, Inc. 
Mail: 9 Post Ave., New York 34, N.Y. 
(M) 

Bassett, Fred E., Jr., Motion Picture, 
Sound and Projection Engineer, RCA 
Service Co., Inc. Mail: 1131 Venetia 
Ave., Coral Gables, Fla. (M) 

Boyers, John S., Engineer, Magnecord, 
Inc., 225 W. Ohio St., Chicago 10, 
111. (A) 

Brown, Freeman H., Director, Photo 
Laboratory, The University of Wis- 
consin. Mail: 1204 West Johnson 
St., Madison 6, Wis. (A) 

Clemson, Stanley L., Sound Engineer, 
Queensway Studios. Mail: Valley 
Farm Rd., Pickering, Ontario, Canada. 
(M)_ 

Cummings, Wilbur H., Radio and Tele- 
vision Broadcasting, American Broad- 
casting Co. Mail: 427 Cottage Ave., 
Glen Ellyn, 111. (M) 

Downs, Charles W., Jr., Free-lance 
Assistant Cameraman. Mail: 1060 
Hunter Ave., Pelham Manor, New 
York. (A) 

Dunkelman, Gerald F., Sound Engineer, 
RCA Service Co., Inc. Mail: 194 
Oakdale St., Staten Island 12, N.Y. 
(A) 

Frank, Emil H., Television Executive. 
Mail: 550 Fifth Ave., New York, N.Y. 
(A) 

Harding, H. Theodore, Motion Picture 
Product Manager, E. I. du Pont de 
Nemours & Co., Inc., 1450 Nemours 
Bldg., Wilmington, Del. (M) 

Indjian, Daniel, University of Southern 
California. Mail: 1470 S. Shenandoah 
St., Los Angeles 35, Calif. (S) 

Irvine, William L., Photographer, Corps of 
Engineers, U.S. Army. Mail: 2919 
South 8th St., Kansas City 3, Kan. (M) 

Kaplan, Richard, Dept. of Cinema, 
University of Southern California, Los 
Angeles 7, Calif. (S) 

Koppel, Leo, Works Director, Ship Car- 
bon Co. of Great Britain, Ltd. Mail: 
51 Mount Pleasant Rd., Chigwell, 
Essex, England. (A) 

Lummis, Oscar W., Sound Engineer, 



Associate (A) 



Student (S) 



RCA Service Co. Mail: 3009 Magee 
.Avenue, Philadelphia 24, Pa. (A) 

Mahon, John C., Jr., Instructor, Motion 
Picture Photography, University of Cali- 
fornia at Los Angeles. Mail: 6608 
Jamieson Ave., Reseda, Calif. (A) 

Marcus, Joseph, Engineer, Federal 
Manufacturing and Engineering Corp. 
Mail: 1269 E. 89 St., Brooklyn 36, 
N.Y. (M) 

Mathiesen, George H., Television Engi- 
neer, KPIX, Inc. Mail: 301 Ricardo 
Rd., Mill Valley, Calif. (A) 

Meyer, H. J., Factory Representative, 
West Coast, Wollensak Optical Co. 
Mail: 1260 Lago Vista Dr., Beverly 
Hills, Calif. (M) 

Pedersen, Raymond L., University of 
Hollywood. Mail: 930 N. Edgemont 
St., Los Angeles, Calif. (S) 

Polito, Eugene E., Free-lance Cinema- 
tographer. Mail: 1456 N. Ogden Dr., 
Hollywood 46, Calif. (M) 

Rella, Fred A., Motion Picture Production 
Supervisor, New York State Dept. of 
Commerce, Motion Picture Unit, 40 
Howard St., Albany, N.Y. (M) 

Rogan, Barney B., Electrical Technician 
& Sound Recordist, Mode-Art Pictures, 
Inc. Mail: R.D. #12, Pittsburgh 29, 
Pa. (A) 

Schick, Elliot, Producer-Director, TV 
Films, President, Nova Productions, Inc. 
Mail: 179 West St., New York 7, N.Y. 
(A) 

Sheldon, Irwin R., Design Engineer, Pre- 
cision Laboratories. Mail: 300 Ocean 
Parkway, Brooklyn 18, N.Y. (A) 

Waner, John M., Motion Picture Film 
Dept., West Coast Div., Eastman Kodak 
Co. Mail: 4112 Arch Dr., North 
Hollywood, Calif. (A) 

Welty, Thomas D., Assistant Construction 
& Operating Engineer, School of Music, 
Motion Picture and Broadcasting 
Studios, University of Washington. 
Mail: 12047 14th Ave., N.E., Seattle 
55, Wash. (A) 

Wolff, Alfred, Cinematographer, Lecturer. 
Mail: 3426 Elaine Place, Chicago, 111. 
(A) 

CHANGE OF GRADE 

Gavey, Thomas W., Captain, U.S. Air 
Force. Mail: P.O. Box 2610, Wash- 
ington, D.C. (A) to (M) 



86 



Chemical Corner 



Edited by Irving M. Ewig for the Society's Laboratory Practice Committee. Sugges- 
tions should be sent to Society headquarters marked for the attention of Mr. Ewig. 



New Uses of Glycerine An article by 
M. A. Lesser in 

the October 1 949 issue of Commercial Photog- 
raph}- describes some interesting uses of 
glycerine for removing negative scratches 
and as a wetting agent in developers for 
aiding the elimination of streaks. 

Non-Skid Floor Wax "Cetox" is a high- 
gloss floor wax 

which is slip proof whether it is wet or dry 
because it's "hydraoxated." This product 
has the UL label and is manufactured by 
Chemical Service of Baltimore, Howard 
and West Streets, Baltimore 30, Md. 

Fireproofing "Ruflan" is a flame re- 
tardent spray of plastic 
made by E. I. DuPont. 

To Keep Chemicals Dry and Uncon- 
taminated A con- 

venient drum cover made of paper contain- 
ing Neoprene. This is superior to wooden 
barrel heads and fiber covers or even metal 
drum lids for keeping chemicals in con- 
tainers dry and in an uncontaminated 
condition. They are very easy to get on 
and off. The vendors are the Chase Bag 
Co., 1500 South Delaware Avenue, Phila- 
delphia, Pa. 

Disinfectant Soaps The Davies Young 
Soap Company, 

Dayton, Ohio, makes a concentrated soap 
with a high germicidal effect, "Germelin," 
which should be excellent for washing de- 
veloping and water tanks and would go a 
long way toward the elimination of that 
Monday morning smell. 

Prevention of Slime in Wash Tanks 

"Algex" is a phe- 
nolic derivative sold 

by the L. B. Russell Chemicals, Inc., of 60 
Orange Street, Bloomfield, N.J. It is a 
good destroyer of slime and algae growths 
found frequently in wash tanks. It comes 
in convenient tablets which can be dropped 
in the bottom of the tank near the water 
inlet. 



Stable Color Developer "Genochrome" 
is a derivative 

of p-aminodiethylaniline which has greater 
resistance to aerial oxidation and is less 
toxic than most color developers. The 
article describing this appears in The Royal 
Photographic Society Color Group Bulletin, No. 
13. It is written by G. T. J. Field and 
D. H. O. John. 

Conservation of Water Washing of film 
serves a dual 

purpose. The first is to remove soluble 
silver salts because, if allowed to remain, 
these cause staining and discoloration. 
The removal of silver salts is best insured 
by a two-bath system of fixation. The 
second function of washing is the removal 
of hypo. If allowed to remain in excessive 
concentrations will result in fading and dis- 
coloration. 

The reduction of the hardening proper- 
ties of the fixer, maintaining the wash water 
at as high a temperature as possible, ade- 
quate agitation, frequent changes of wash- 
ing, avoiding contamination of each wash 
section by the use of squeegees, all aid in the 
reduction of the quantity of water required 
for washing. A complete story of this may 
be found in the article byj. I. Crabtree, 
"How to Save Water," appearing in The 
Photographic Science and Technique Journal, 
Section B, August 1950, pages 70-74. 

Flow Meter The Builders-Providence 
Company, 419 Harris Ave., 
Providence 1, R.I., has designed a com- 
pact, easily installed, self-contained and 
self-operated flow meter, "Propeloflo." 
The flow through main or auxiliary pipe- 
lines is all that is needed to run this meter 
no mercury, pressure piping, or electrical 
connections are required. 

Make Your Own Distilled Water "Filtr- 

lon" is 

a new and refillable ion-exchanger unit 
for small quantity uses which delivers water 
equal to triple distilled water. It is 
manufactured by LaMotte Chemical Prod- 
ucts Co., Baltimore 4, Md. 



87 



This May Solve Your Dust Problem 

An easily applied, 
stainless "dust sealer" made by the West 
Disinfecting Co., 46-16 West St., Long 
Island City, N.Y., reduces dust to a mini- 
mum by leaving an antiseptic film to which 
dust adheres. This film is then easily 
removed. One gallon covers 4,000 sq ft. 

New Products 



A New Adhesive Tape This product is 
called #666 

arid is made by The Minnesota Mining 
Company. It is cellophane tape coated on 
both sides with adhesive for which many 
uses may be found in the laboratory. It 
does not fog or desensitize photographic 
material. 



Further information about these items can be obtained from the addresses given. As in 
the case of technical papers, the Society is not responsible for manufacturers' statements, 
and publication of news items does not constitute an endorsement. 




The Utiliscope is a closed-circuit television 
system developed by Diamond Power 
Specialty Corp., Lancaster, Pa. Sim- 
plicity in circuits and controls is a basic 
feature of this industrial instrument. The 
receiver is a Farnsworth cold cathode, 
image-dissector, camera tube. The com- 
plete system of camera, power supply and 
monitor as shown in the illustration is de- 
signed for portability and weighs 110 Ib. 
The power supply can be placed as far as 25 
ft from the camera and the monitor can be 
up to 1000 ft away. The lens used as 
standard equipment is 90-mm, //1. 4, 
coated, focused by rack-and-pinion gear. 
A remote focusing drive can be incorpo- 
rated, however. 

Only 17 tubes, including the camera 
tube, are employed. A 10-in. picture tube 
is standard but 12- or 16-in. tubes can be 



substituted. The system has a 300-line 
resolution. 

A trial use of the Utiliscope in a Holly- 
wood motion picture studio is reported by 
W. W. Herlihy, Sales Service Engineer for 
the Diamond Power Specialty Corp. The 
possible effectiveness of a particular movie 
set for a forthcoming circus production was 
tested with the Utiliscope camera and 
power supply suspended on a small trapeze 
opposite the performers' trapeze in prefer- 
ence to building a scaffold to support a 
studio camera and two cameramen. A 
mannequin was used as the stand-in and 
the motion picture of the swinging trapeze 
was transmitted from the swinging camera 
to the receiving unit on the floor. After 
this inexpensive preview the director de- 
cided to abandon the scene, having in- 
curred very little expense for the rejected 
shot. 



88 



Data on Random-Noise Require- 
ments for Theater Television 



By PIERRE MERTZ 



Provisional evaluation of permissible random noise for theater television is 
considered from several sources of information. These cover broadcast tele- 
vision experience and the graininess in motion picture film; the requirements 
deduced from the various sources generally agree. For broadcast television, 
a frequency weighting and limit on weighted noise power have been used. 
The finer picture detail of theater television presumes a lower permissible 
random noise. Changes in weighting curve are discussed. A limit figure of 
noise is suggested, which is comparable to graininess effects in motion pictures, 
though slightly more severe than present published performance on camera 
tubes. 



1. Introduction and Digest of Conclusions 

A DEFINITIVE EVALUATION of the ran- 
dom noise which is permissible in the- 
ater television will need to be made, 
of course, with theater television equip- 
ment. In the meantime, certain deduc- 
tions can be drawn from other sources to 
permit the estimate of a provisional figure 
which can eventually be checked. 

In the first place, data can be ex- 
amined, which have been obtained for 
the setting of random-noise require- 
ments for 4-mc broadcast television. 
Though the solution of this problem is 
not definitive either, experience with it 
has indicated that at present the best, 
simple answer consists in weighting the 
frequency distribution of the random 
noise, and measuring the rms amplitude 
of the weighted noise wave, as compared 

Presented on May 1, 1951, at the Society's 
Convention in New York, by Pierre Mertz, 
Bell Telephone Laboratories, Inc., 463 
West St., New York 1 4. 



with the peak-to-peak amplitude of the 
television video signal (from tip of syn- 
chronizing pulse to maximum white 
level). Then the effect of varying 
amounts of weighted noise upon a pic- 
ture is submitted for judgment to a 
group of observers. They are given a 
set of preworded comments to use as 
criteria of impairments. The list is 
reproduced below. 

1. Not perceptible; 

2. Just perceptible; 

3. Definitely perceptible, but only 
slight impairment to picture; 

4. Impairment to picture, but not 
objectionable; 

5. Somewhat objectionable; 

6. Definitely objectionable; and 

7. Not usable 

To be noted, particularly, are com- 
ments No. 2, "just perceptible," and 
No. 4, "impairment to picture, but not 
objectionable." 

With a picture of excellent quality by 



August 1951 Journal of the SMPTE Vol. 57 



89 



LEGEND 

OVER ALL 
SMOOTHED RESULTS 




O.I 1.0 10 25 50 75 90 99 99.9 

PER CENT OF OBSERVATIONS AS INDICATED FOR GIVEN NOISE 

Fig. 1. Characterization of random noise on a television image. 



present-day broadcast criteria, and using 
the 525-line and other current standards, 
and with the picture viewed at four 
times picture height, the pooled data on 
noise evaluation for three picture sub- 
jects are plotted, as smoothed for 
engineering use, in Fig. 1 . 

Examination of this shows that at a 
weighted noise somewhere between 40 
and 50 db below the signal, 50% of the 
observers voted "comment No. 2 or 
less," i.e., they just begin to perceive the 
noise. Ninety per cent of the observers 
voted "comment No. 4 or less," i.e., the 
remaining 10% are just becoming con- 



scious of the objectionable character of 
the noise. A figure of 46 to 47 db for the 
weighted noise has sometimes been used 
as an overall design objective. This 
corresponds to a figure of 44 db un- 
weighted noise of flat distribution, or 40 
db, if the distribution is "uptilted" or 
peaked toward the upper frequencies. 

The weighting function to be used 
with Fig. 1 is again not definitive, but 
some of our best knowledge of it at 
present is plotted as curve I of Fig. 2. 

The discussion which is presented be- 
low leads to the conclusion that for an 
8-mc theater television system exactly 



90 



August 1951 Journal of the SMPTE Vol. 57 




\ 



\ 



Dl STRI BUTIONS 

UPTILTED 
NOISE 



FLAT 
NOISE 



WEIGHTING 
FUNCTIONS 

m 
n 

i 



.6 .8 1.0 2 

VIDEO FREQUENCY- Me 



Fig. 2. Weighting functions and random-noise distributions. 



the same plot as shown in Fig. 1 can be 
used provisionally. The weighting func- 
tion to be used, however, is that indicated 
by curve III of Fig. 2. These indica- 
tions assume that the system uses in the 
order of 740 scanning lines. If the 
broadcast standard of 525 lines is con- 
tinued, and the frequency band merely 
widened to 8 me, the weighting curve I is 
to be used, but the acceptable weighted 
noise reduced 3 db, i.e., the plots of Fig. 1 
can be used, with the figures marked in 
the ordinates all increased numerically 
by 3 db. 

These deductions all contain, either 
implicitly in the new weighting function 
or explicitly where the same weighting 
function continues to be used, a factor of 
3 db greater severity in the requirement 
imposed. This is an estimate of the 
influence of the higher quality of the 
8-mc theater television image (in the 
form of increased sharpness) as com- 
pared with the 4-mc image on which the 
data were taken. 

Analogous figures have been reported 
by RCA, reached by means of a different 
philosophy, as will be discussed below. 



Their figure, translated into the terms 
which have just been used, is 50 db. 

An obvious comment which can be 
made on the experiments used for plot- 
ting Fig. 1 is that they were carried out 
on a screen which was adequate in size 
for the testing of home viewing of broad- 
cast television, but which was too small 
for the testing of theater television. 
There is evidence to show, however, that 
if the image subtends the same angle at 
the eye (which is controlled by setting the 
ratio of viewing distance to picture 
height), the results are very little de- 
pendent upon its absolute size. 

A second estimate of permissible ran- 
dom noise in theater television pictures 
can be deduced from a study of the 
photographic graininess in present-day 
motion pictures. Although this graini- 
ness is perceptible to a watchful observer 
in a good seat, it is not obtrusive and not 
considered a problem by the motion pic- 
ture industry. It can, therefore, serve 
as an index of how much of this impair- 
ment is acceptable. A simple deduction 
on the amount of this noise as derived 
from sound-track measurements indi- 



Pierre Mertz: Random Noise 



91 



cates a weighted signal-to-noise ratio, in 
television terms, of 47 to 52 db. Otto 
Schade of RCA has shown, however, 
that this deduction ignores certain im- 
portant points. When these are taken 
into account, the result is not as definite, 
but the figures, less severe, are not 
changed by more than 2 or 3 db. 

A third check to be made against 
these figures is the random noise being 
delivered by camera tubes available at 
present. The performance of these, of 
course, varies a great deal with the condi- 
tions of use, the adjustments and the 
individual tube being used. Some typi- 
cal figures published by RCA (in addi- 
tion to some informal information) give 
signal-to-noise ratios which, when trans- 
lated into the same terms as used above, 
are, for broadcast television use, those 
shown in Table I. 



Table I 

Signal- (peak-to- 
peak, including 
synch, ) to-weighted 



Camera tube 



noise ratio 



1850A iconoscope 44 db 

5655 image orthicon 44 db 

5769 image orthicon below above figure 

5820 image orthicon 40 db 

5826 image orthicon 43 db 

1848 iconoscope 39 db 

2P23 image orthicon 36 db 



The best of these, therefore, formally miss 
the tentative overall design objective by 
2 or 3 db, without allowance for contri- 
bution to noise from any other sources. 
It should be understood, of course, that 
new tubes are likely to be under develop- 
ment with better figures on noise per- 
formance. 

A Bell Laboratories film scanner gives 
a signal-to-weighted noise ratio, in the 
above terms, estimated at 46 db. The 
data of Fig. 1 were taken with this signal 
source and, as taken, follow approxi- 
mately the dotted lines. The solid 



lines represent an estimate in which the 
ordinates cover total noise (i.e., signal 
generator noise plus applied noise). 

The indications as a whole from this 
third check are, therefore, that for 
theater television the random noise will 
be a problem not only for the connecting 
links, but also for the pickup apparatus. 

2. Use of 4-Mc Data 

Some data have been taken on noise 
requirements for 4-mc broadcast tele- 
vision channels, and a first approxima- 
tion of the theater problem can be de- 
rived from them. 

The major difference, of course, be- 
tween the 8-mc and the 4-mc channels 
lies in the sharpness of the resulting pic- 
ture. One may expect, consequently, 
that the viewer will measure the random 
noise against the finest detail which it 
obscures or distorts, and therefore to that 
extent he will be more critical of the 8-mc 
than of the 4-mc random noise. One 
can even propose, as probably reason- 
able, a principle that the viewer will con- 
sider equally objectionable, equal rms 
amplitudes of a "flat" distribution of 
random noise up to cutoff in the 4-mc 
channel and a similar "flat" distribution 
to cutoff in the 8-mc channel. This will 
be referred to below a number of times 
and will henceforth be merely called 
"the proposal." At the same viewing 
distance, the 8-mc band granulation 
would obviously be less visible than the 
4-mc band granulation of the same 
amplitude, and the proposal amounts to 
making this difference in visibility a 
quantitative estimate of how much more 
critical the observer is in the case of the 
8-mc picture than he is in the case of the 
4-mc picture. If the proposal is taken 
as a guide, it means that with a "flat" dis- 
tribution the total noise power in the 8- 
mc channel would be set at the same 
value which is acceptable for the 4-mc 
channel. This means that the tolerable 
noise power per kc of bandwidth is set at 
3 db lower in the 8-mc than in the 4-mc 
channel. 



92 



August 1951 Journal of the SMPTE Vol. 57 



M. W. Baldwin discovered experi- 
mentally, some time back, 1 that in a 
given television system the impairing 
effect of a flat "low-pass" distribution of 
random noise is measured largely by the 
noise power per kc, and is substantially 
independent of the upper cutoff. This 
means that if one uses this measure of 
how much more critical the viewer is 
expected to be, according to the proposal, 
of 8-mc than of 4-mc television, it 
amounts to a 3-db difference in admis- 
sible random noise. In the same ex- 
perimentation it was also found that 
for equal impairing effect the random- 
noise power is raised 6 db for a doubling 
of the viewing distance. A measure of 
the expected reaction in the observer, 
according to the proposal, therefore, 
also corresponds to a reduction, in the 
ratio of 1 to \/2^in the minimum viewing 
distance for which the system is to be 
engineered for 8 as compared to 4 me. 

There are other grounds for consider- 
ing the proposal to be reasonable. 
These are that the added fine detail 
signal in going from a 4-mc to an 8-mc 
band is lower on a power-per-kc basis 
than the signal already existing in the 
4-mc band. General typical indications 
are that the average signal power per kc 
at 8 me is J that at 4 me. The average 
power per kc of the added signal would, 
therefore, be somewhere between equality 
and J of that at the 4-mc cutoff. The 
noise power per kc in the band between 
4 and 8 me, for the 8-mc system, as set 
by the proposal, is just half that in the 
4-mc system. Half happens to be the 
mean proportion between 1 and ^. 
Thus, on the new detail, added between 
4 and 8 me, the signal-to-noise ratio, to at 
least its mean proportional, is kept at the 
figure maintained in the 4-mc system at 
4 me. There is, of course, an improve- 
ment of 3 db in the signal-to-noise ratio 
between and 4 me, which is one of the 
factors contributing to the improved 
quality of the 8-mc over the 4-mc system. 
The consequences of the proposal, when 



increasing the bandwidth from 4 to 8 
me, may be examined in more detail. 

For Case I it will be assumed that the 
number of scanning lines is not changed 
in going from 4 to 8 me. Diagrams of 
the two observed pictures are illustrated 
in Fig. 3, each viewed at four times pic- 
ture height. The scanning-line struc- 
ture will be identical in the two cases. 
The finest horizontal detail that can be 
seen in the 8-mc picture at (b) is, how- 
ever, twice as fine as in the 4-mc picture 
at (a). This is indicated schematically 
by marks which are proportional to cycle 
marks in the two. At (a), the 4-mc 
cycle marks will have exactly twice the 
spacing that the 8-mc marks have at (b) . 

The theory that was presented in the 
paper on "Perception of Television Ran- 
dom Noise," 1 indicates that the simpli- 
fied noise-weighting curve presented 
there for a four-times-picture-height view- 
ing distance is merely extended from 4 to 
8 me. This is illustrated by curve I of 
Fig. 2. It is to be noted, by reference to 
the original paper, that under the condi- 
tions then used in the experiment most 
of the weighting was visual, i.e., in the 
eyes of the observer. The picture tube 
used contributed somewhat, estimated at 
about a third to a quarter of the final 
effect. In Fig. 2 this double source of 
the weighting is ignored. 

For Case II it will be assumed that the 
number of scanning lines in the 8-mc 
system is increased, in the ratio of -\/ 2 
to 1 , to that in the 4-mc system. This is 
illustrated in Fig. 4. Fig. 4(a) is merely 
a duplication of Fig. 3 (a). The solid 
lines in Fig. 4(b) are a duplication of 
Fig. 3(b), except for the cycle marks. 
Since the number of scanning lines has 
been increased in the ratio \/ 2 to 1 , the 
horizontal speed of tracing them has been 
increased in the same ratio. Thus, the 
8-mc cycle marks no longer have half the 
spacing of the 4-mc cycle marks in (a) ; 
they now have I/ -\/ 2 times the spacing 
of the latter. 

Inside of Fig. 4(b), in dotted outline, is 



Pierre Mertz: Random Noise 



93 



a picture frame that covers the same 
number of scanning lines vertically as 
used in the 4-mc system of Fig. 4(a). It 
therefore has \f \/ 2 times the vertical 
height of the picture in solid lines. The 
remainder of the picture frame is drawn 
in to the same scale, i.e., its width is 
1 / \/ 2 times that of the one in solid 
lines. The cycle marks are shown with 
exactly the same spacing as the 8-mc 
cycle marks in the picture with solid 
lines. 

It will be noted that, except for its 
absolute size, which is reduced in scale in 
the ratio of 1 to \/ 2, the dotted-line 
picture of Fig. 4(b) has exactly the same 
objective capabilities for rendering de- 
tail, with the 8-mc band, that Fig. 4 (a) 
has with its 4-mc band. It will also 
objectively render random noise in ex- 
actly the same way, provided the in- 
stantaneous time scale of the noise is 
stretched in the ratio of 2 to 1 , because 
the cycle marks at 8 me in Fig. 4(b) have 
exactly the same proportionate spacing 
to the frame that they have in Fig. 4 (a) 
at 4 me. The dotted picture in Fig. 
4(b) is viewed at 4 \/ 2 = 5.65 times 
picture height. Thus, noise will be seen 
in Fig. 4(b) in exactly the same way as in 
the 4-mc picture of Fig. 4 (a) viewed at 
5.65 times picture height, but with the 
noise-frequency scale stretched from 4 
me to 8 me. If the source of the weight- 
ing is ascribed to the eyes of the observer 
alone, and the picture-tube contribution 
ignored, the noise-weighting curve for 
Fig. 4(b) is that for Fig. 4 (a), viewed at 
5.65 times picture height, stretched on 
the frequency scale so that the 4-mc 
point appears at 8 me. This weighting 
curve is shown at II in Fig. 2. 

We do not contemplate setting the 
noise for the 8-mc channel in Fig. 4(b) 
equal in absolute perceptibility to that 
for the 4-mc channel in Fig. 4 (a), but it 
will be of some interest to examine what 
this leads to. 

What is involved in the proposal, in 
terms of Fig. 4(b), is to engineer the 8- 



mc system in terms of a viewing distance 
that permits the fine detail in the dotted- 
line frame to be equal to that seen in 
Fig. 4 (a). This is accomplished by re- 
ducing the viewing distance to 4/ \/ 2 or 
to 2.83 times picture height. This has 
been done in Fig. 5(b) and will represent 
Case III. 

Figure 5 (a) is again a duplication of 
Figs. 3 (a) and 4 (a). The dotted-line 
picture in Fig. 5(b) is also exactly th * 
same in objective representation of de- 
tail. The dotted cycle marks in Fig. 
5(b) are spaced exactly the same as in 
Fig. 5 (a), but represent 8-mc cycles in- 
stead of 4-mc cycles. Then the solid 
lines in Fig. 5(b) are scaled up in the 
ratio of the V 2 to 1 about the dotted 
lines, except for the cycle marks, which 
are kept at the same 8-mc spacing. The 
solid lines represent the complete picture 
transmitted by the 8-mc band viewed at 
2.83 times picture height, according to 
the consequences of the proposal. The 
noise-weighting curve for Fig. 5(b) is, 
therefore, the same as that used for Fig. 
5 (a), except that it is stretched along the 
frequency scale so that the 4-mc point 
appears at 8 me. This is shown by 
curve III in Fig. 2. 

With this background, relations be- 
tween the various cumulated weighted 
power requirements can be deduced for 
the three cases considered, first, under 
assumptions of equal absolute noise per- 
ception between the 4- and 8-mc bands, 
and then, under the proposed assump- 
tion of a somewhat more severe require- 
ment for the 8-mc band. To correlate 
the results with two distributions of 
noise, approximated in practice, the 
weighted power ratios can then be trans- 
lated into unweighted power ratios for 
those distributions. The distributions 
are illustrated in Fig. 2; they are the 
"flat," already mentioned, and the 
"uptilted," rising with frequency up to 
the cutoff point at the rate of 6 db per 
octave. The relations have been sum- 
marized in Table II. 



94 



August 1951 Journal of the SMPTE Vol. 57 



4 Me 



8 Me 




4 x PICTURE 
HEIGHT 




Fig. 3. Viewed 4-mc (a) and 8-mc (b) pictures. 
No change in scanning lines. 



4 MC 




4 x PICTURE 
HEIGHT 




-5.65 x P. H. 



Fig. 4. Viewed 4-mc (a) and 8-mc (b) pictures. Scanning- 
line ratio 1 : V2- No change in viewing distance. 



4 Me 



A X PICTURE 
HEIGHT 




2.83 x PICTURE 
HEIGHT 




Fig. 5. Viewed 4-mc (a) and 8-mc (b) pictures. Scanning- 
line ratio 1: \/2. Vie wing-distance ratio ^2ll. 



Pierre Mertz: Random Noise 



95 



Table II 



Cases 



II 



III 



A. Weighted 

Equal absolute perception 

Flat or uptilted noise, 8 me above 4- 

mc* power db 1 .5 db 

Proposal 

Flat or uptilted noise, 8 me above 4- 

mc* power -2.8 db 

B. Unweighted 
Equal absolute perception 

Flat noise, 8 me above 4-mc* power 2.8 2.8 

Uptilted noise, 8 me above 4-mc* 

power 6.4 4.7 

Uptilted above flat noise, 4 me 3 . 5 

Uptilted 8 me, above flat 4 me* 9.9 8.2 

Proposal 

Flat noise, 8 me above 4-mc* power 

Uptilted noise, 8 me above 4-mc* 

power 3.6 

Uptilted 8 me, above flat 4 me* 7.1 3.5 

* Distribution up to 4 me using the weighting of Case I 



The basic data from which the items 
in the table are calculated are given in 
the Appendix. Explanations of the 
calculations are outlined immediately 
below. 

For absolute equal perception in Case 
I, the weighted noise, either flat or up- 
tilted, should be the same for the 4 and 8 
me, this, of course, being the objective of 
the weighting. For Case II, the closer 
scanning lines in Fig. 4(b) as compared 
with Fig. 4 (a), which can also be 
measured by the difference in viewing 
distances, lead to a rise of 1.5 db in 
weighted noise from the 4- to the 8-mc 
band. This can be determined from 
equation (5) of reference 1 . 

For the proposal, the objective in Case 
I, as has been noted, is to set the un- 
weighted cumulated flat noise require- 
ment the same for the 8- as for the 4-mc 
band. The weighting to a sharp cutoff 
at 4 me reduces the total power by 2.87 
db as compared with the unweighted 
power (to the same sharp cutoff). The 
weighting to a sharp cutoff at 8 me re- 



duces the total power by 5.64 db as 
compared with the unweighted power. 
Thus, application of the proposal leads 
to the requirement for the 8-mc channel 
of a weighted total noise power which is 
5.64 - 2.87 = 2.77 db lower than for the 
4-mc channel. In each case the same 
curve I of Fig. 2 is used as the weighting 
function. 

The objective in Case III is to set the 
requirement for the 8-mc weighted noise 
(with the weighting of curve III) at the 
same value as for the 4-mc weighted noise 
(with the weighting of curve I). This 
ratio then holds for other distributions of 
noise, including "uptilted." 

Taking up the first item under B, in 
the table, under Case I and from the 
Appendix, the drop for flat noise in 
weighted power from unweighted is 2.87 
db for 4 me, and 5.64 db for 8 me. 
Thus, the net permissible rise in un- 
weighted power, from 4 to 8 me, is 
-2.87 + 5.64 = 2.77 db. For Case II 
the respective figures are 2.87 and 
+4.21 db, but there is a differential of 



96 



August 1951 Journal of the SMPTE Vol. 57 



1.5 db in weighted power, giving 
-2.87 + 4.21 + 1.5 = 2.84 db. 

For uptilted noise the corresponding 
figures are -6.34 + 12.72 = 6.38 db for 
Case I, and -6.34 + 9.56 + 1.5 = 4.72 
db. 

At 4 me the permissible unweighted 
uptilted noise, above flat noise, is 6.34 - 
2.87 = 3.47 db. At 8 me the permissi- 
ble unweighted uptilted noise, above 
flat noise at 4 me, is 12.72 - 2.87 = 9.85 
db, for Case I. For Case III, it is 9.56 - 
2.87 + 1.5 = 8.19 db. 

In the next group of items, covering 
the proposal, the first comes back to the 
original objective for Case I, namely 
that the 8-mc flat unweighted noise be 
placed at the same level as the similar 4- 
mc noise. For Case III, the weightings 
to 8 me on curve III and to 4 me on 
curve I give the same drop from flat un- 
weighted to weighted noise, namely 2.87 
db. This keeps the difference zero for 
the unweighted, as it did for the weighted 
noise. This also holds for uptilted noise 
in Case III, the drop here being 6.34 (or 
6.35) db for each. For Case I, on this 
last item, the figures are 12.72 6.34 - 
2.77 = 3.61 db. 

Finally, the uptilted 8-mc noise, above 
flat 4-mc noise, each unweighted and for 
Case I, is 3.61 + 3.47 = 7.08 db. For 
Cafse III, the figures are + 3.47 = 3.47 
db. 

It is to be understood, of course, that 
the small fractions of db which are kept 
in the figures above are purely for the 
sake of internal consistency in the table, 
and do not pretend to imply such pre- 
cision in knowledge of the correct 
weighting. 

There have been many analyses of the 
random noise permissible in a broadcast 
television channel. Perhaps the most 
comprehensive of recent tests were 
carried out together with others pre- 
sented in a paper 3 before the IRE Con- 
vention in March 1950. The reactions 
of observers to random noise in a tele- 
vision picture were determined, as ex- 
pressed by preworded comments. The 



signal used followed the 525-line and 
other current broadcast standards. The 
pictures were observed under critical 
viewing conditions and were of excellent 
quality as considered by present-day 
broadcast television criteria. The high- 
light luminance and contrast ratio 
varied from picture to picture, in order 
to adjust to the best image in each case. 
The first ranged from 42 to 65 mL, and 
the second, from 26 : 1 to 130 : 1. The 
resulting data are shown summarized in 
Fig. 1 . The dotted lines cover the effect 
of noise already existing in the film 
scanner used to generate the signal, and 
can be ignored for the moment. They 
will be discussed again below in connec- 
tion with the noise originating in pickup 
devices. 

The ordinates of Fig. 1 are plotted as 
signal-(peak-to-peak, including syn- 
chronizing pulses) to-weighted rms noise 
(weighted according to curve I of Fig. 2) 
ratio. Following the proposal made 
above, the curves can be used as they 
stand for the 8-mc band, if the noise is 
weighted according to curve III of Fig. 
2, provided the number of scanning lines 
in the 8-mc system is raised from 525 to 
741. If the number of lines is kept at 
525, then according to the discussion the 
acceptable weighted noise power is re- 
duced by 2.7 db. That is, the ordinates 
should be labeled with figures numeri- 
cally 2.7 db (say, rounded to 3 db) 
greater, and the weighting curve I of 
Fig. 2 used. 

The data for Fig. 1 were taken on a 
television picture 6 X 8 in., and it would 
be natural to question them for applica- 
tion to a theater-screen-size picture, even 
if the solid angle subtended at the eye 
were the same. In 1941 there were 
doubts of a similar kind, directed par- 
ticularly at the sharpness perception of 
the observer to detail in the picture. 2 
These existed particularly because of 
earlier data indicating a loss of visual 
acuity for near vision. The 1941 results 
indicated the earlier information to have 
been much exaggerated, and perception 



Pierre Mertz: Random Noise 



97 



to be fairly closely the same over the visual 
range of accommodation. The change 
in visual acuity, according to Luckiesh 
and Moss, is about 16%, and, according 
to unpublished experiments of Baldwin, 
about 4%. While data on the larger 
screen are eventually desirable, the 
curves of Fig. 1 are acceptable provi- 
sionally. 

3. Photographic Graininess Data 
(Sound Track) 

Film graininess has been an important 
problem for the motion picture engineer 
from the start, and there is much litera- 
ture on the matter. 4 Simple quantita- 
tive data on the subject come from the 
use of film for sound track, of the vari- 
able-density type. A brief review of the 
data are given in an unpublished report 
presented by Dr. Otto Sandvik to the 
Subcommittee on Distribution Facilities 
of the Committee on Theater Television 
of the SMPTE. 

The sound track is scanned by an 
aperture, 0.084 in. wide and 0.001 in. 
long (i.e., in the direction of motion). 
The sound system transmission is sub- 
stantially flat from 50 cycles to 10 kc. 
The signal-to-noise ratio on such a sys- 
tem is of the order of 45 db. This is 
under optimum conditions, and it is 
more likely to be of the order of 40 db. 
These are the basic figures, before 
schemes of noise reduction, which cannot 
be employed in the picture, are used. 

In order to interpret these figures in 
terms of pictorial representation it is 
necessary to know how the noise and 
signal are measured. The noise is 
measured by its rms amplitude. The 
signal is measured by the rms amplitude 
of a sine wave that is printed at an 
average diffuse density which is under- 
stood to be of about 0.6 in the film 
(transmission 25%) and to have an 
order of 8-db margin against a sine wave 
whose peaks just saturate on the zero 
transmission side. The usual method of 
expressing this ratio in the television art 
is to measure the noise by its rms ampli- 



tude, as here, but the signal is measured 
by its peak-to-peak amplitude. In a 
general way, the picture in a film runs 
from nearly zero transmission to some 
80% transmission. Thus, the following 
corrections are needed to translate from 
the sound signal to the picture signal: 

3 db rms to peak-to-zero 

6 peak-to-zero to peak-to-peak 

8 margin, peak-to-peak 

4 50% to 80% transmission range 
21 db total 

In addition, television measurements 
are usually expressed with respect to a 
signal wave including the synchronizing 
pulse, which is some 2.5 db greater in 
peak-to-peak amplitude than a signal 
wave including only the picture. Thus, 
this figure should be added, giving a 
final correction of 23.5 db. This gives 
68.5 db and 63.5 db, respectively, for the 
optimum and typical figures. 

The next step involved in the inter- 
pretation is to correct for the aperture 
spot size, which is, of course, not the 
sound-track scanning-aperture size. An 
8-mc theater television system of 741 
lines (525 \/ 2) will be assumed. This 
has 700 unblanked lines, and there are 
590 half-cycles of the 8-mc wave along 
the unblanked length of a scanning line. 
Thus, the aperture spot size as measured 
on the film is 0.905 X 1.46 mils. It has 
an area of 1.32 sq mils, as compared 
with the 84 sq mils of the sound-track 
aperture. Graininess distribution is 
approximately a normal distribution, 4 
or its spectrum is approximately flat, so 
that the power ratio correction is very 
closely the area correction. This is 64 
to 1, or 18 db, which must be subtracted 
from the signal-to-noise ratio which has 
been mentioned above. 

There is an additional correction to be 
made for the difference in repetition rate 
between motion picture frames and com- 
plete television frames, which affects the 
storage of the visual perception. When 
the flicker is imperceptible, this is 



98 



August 1951 Journal of the SMPTE Vol. 57 



approximately in the ratio of the repeti- 
tion rates for the noise power. This is 
30/24, or about 1 db, which changes the 
ISdbaboveto 19db. 

Since the noise spectrum is flat, the 
weighting, with curve III of Fig. 2, re- 
quires a further numerical addition of 
2.9 db, changing the 19 db to 16 db. 

Thus, it is simply deduced that for 
theater television the weighted random 
noise corresponding to motion picture 
graininess is slightly over 52 db under 
optimum conditions, and slightly over 
47 db under more usual release-print 
conditions. 

Dr. Sandvik also refers to some figures 
presented by Otto H. Schade in the RCA 
Review 6 (p. 36, Mar. 1948). These are 
based on a Fechner fraction of 2% [see 
his equation (18)], but are said to be in 
substantial agreement with values ob- 
served on high-quality 35-mm film. 
They come out, respectively, (un- 
weighted) 37 and 33 db, for 500- and 
800-line systems. The signal basis is B, 
or average scene luminance (average 
over the frame). The average, from 
frame to frame, has been investigated 6 
and found, for black-and-white feature 
films, to be of the order of J the maxi- 
mum. It is obviously glib to substitute 
this for the average over the frame, but 
the order of magnitude appears right. 
Thus, there should be added 14 db, plus 
2.5 db for synchronizing signal, less 1 db 
for frame-speed ratios, and plus 2.9 db 
for weighting. The result is slightly 
over 51 db for the 800-line system. This 
is admittedly rough and ready, but in 
agreement with the previous figure. 

It may be noted that Schade, in the 
reference which has just been quoted 5 
has given a further estimate, which he 
entitled "Threshold Signal-to-Noise 
Ratios Required for High Quality" 
(RCA Review, p. 283, June 1948). 
These are for a 4-mc channel rather than 
for theater television, and are not de- 
rived directly from graininess data but 
from threshold visibility on a picture 
tube. They are, nevertheless, of in- 



terest here. They are for a picture of 32- 
ft-L highlight luminance, viewed at four 
times picture height, and do not include 
the 2.5-db allowance for synchronizing 
pulse. The figures are: 

Flat noise 50-54 db 

"Peaked" noise (uptilted) 40-48 db 

These figures are more severe than the 
ones quoted by Sandvik. The figures 
are for unweighted noise, and it is noted 
that the difference ranges from 6 to 10 
db between the uptilted and flat noise 
requirements, as compared with differ- 
ences for the weightings of Fig. 2 ranging 
from 3.4 to 7.1 db. This indicates 
somewhat sharper weighting functions 
than are shown in Fig. 2. 

This difference will be found to occur 
in a number of instances in the present 
report. Examination of the discussion 
of the weighting function by Schade indi- 
cates that he conceives of it as describing 
a filtering phenomenon which is the 
same for single-frequency bars as for 
random-noise grains, and for which he 
has determined the characteristics from 
bar patterns. However, it is to be noted 
that experiments with bar patterns have 
indicated a rise of threshold amplitude 
with frequency 7 (near the upper portion 
of the video frequency range) at the rate 
of 12 db per octave. Experiments with 
random noise 1 (resulting in the weighting 
of Fig. 2) indicate a corresponding rise 
of only 6 db per octave. While the 
question does need to be resolved, the 
weighting of Fig. 2 is considered, for the 
moment, safer than the steeper function 
used by RCA authors. 

Sandvik further refers to some figures 
of Jones and Higgins on granularity. 
These will be discussed in Section 4 be- 
low. 

4. Photographic Graininess Data 
(Picture) 

In a paper presented orally before a 
meeting of the Subcommittee on Inter- 
connecting Facilities, Schade has pointed 
out the oversimplifications in some of the 



Pierre Mertz: Random Noise 



99 



200 



100 
80 



20 




.04 .1 .2 .4 .6 .8 I 

DENSITY, D 

Fig. 6. Graininess variation with density. 
Fine grain Pos. 1302; Neg. 1203 

Plus X - -Super XX 

Straight lines, Schade; points, Jones & Higgins 



deductions in the previous section. 
These are chiefly: 

(a) The grain structure in photo- 
graphic film does not enter into the pic- 
ture, as a function of density, in the 
same manner as does random noise in 
a television picture as a function of 
local luminance (say, measured in terms 
of equivalent density below highlight 
luminance). 

(b) The translation between electrical 
signal voltage and picture luminance is 
not usually linear. 

Schade notes that the law of variation 
of granularity (expressed as a standard 
deviation of local transmittance divided 
by average local transmittance) with 



density, in a single film, is as the square 
root of the latter. That is, 



(1) 



where 



T = transmittance, 

A T standard deviation of transmittance, 
D = density = Iog l0 (l/r), 
ki = a constant. 

He frequently uses the reciprocal R 
T/&T, in which case: 

R = \/(ki \/D}' (2) 

Because photographic graininess follows 
an approximately normal law, R can be 
taken as proportional to the diameter of 



100 



August 1951 Journal of the SMPTE Vol. 57 




.1 .2 .4 .6 .8 I 

DENSITY, D 
Fig. 7. Noise equivalent to graininess variation with density, 



10 



the sampling aperture used in measuring 
the graininess. 

A plot summarizing Schade's meas- 
urements is compared in Fig. 6 with the 
results reported by Jones and Higgins 8 
(p. 203, 1946). The connected points 
were measured by the Selwyn method, 
the isolated points by the Goetz and 
Gould method, and data for various 
sizes of aperture have been corrected to 
that for a diameter of 30/x (1 micron = 
lju = 10~ 6 meter = 10~ 3 mm) for which 
the Schade data are presented. It is not 
likely that the films referred to are the 
same. The intermediate film is known 
to be different, i.e., Plus X for the Schade 
data and Panatomic X for the Jones- 
Higgins data. Considering this, and 
differences in actual samples and de- 
velopment, and also the differences in 



measurements of the same films by two 
different methods, the data of Fig. 6 
represent a good check. 

If the television receiving system re- 
produced picture luminance (or there- 
fore also equivalent transmittance) were 
directly proportional to signal voltage 
and the noise were of a simple additive 
type, then AT in equation (1) would 
be a constant independent of T or D. 
Calling this k%: 



AT = 
R = r/AT 



(3) 
(4) 



Thus, the ratio, R is proportional to T. 
Putting the constant k 2 as 1 , this leads to 
the curve marked n = 1 in Fig. 7, 
which plots relative R as a function of 
density. The curve for this simple con- 



Pierre Mertz: Random Noise 



101 



RELATIVE NOISE AMPLITUDE, AS 
o o o c 

: 


















































































































n 


= 1 
























^* 


*s^Z^ 


z^ 


YN 
















^. 


^>- 






s 


2 


\ 


\ 


\ 












^ 


<^^' 






/ 


,' 


* 




\\ 


\ 










x 


^/' 




/ 


/ 




XPOS 

ONLY 


TIVE 




\ 


\ 




X 


x 


x 


X 


s 


/ 


/ 


/ 










x' 


X 






/ 


y 




























// 




























u 


Y 


























/ 


* 
























.,' / 


/ 


























/ 


7 




























01 .01 .1 .2 .4 .6 .8 1. 
EQUIVALENT TR ANSM 1 T TANCE, T 



Fig. 8. Noise equivalent to graininess variation with transmittance. 



ception of a television system is seen 
to be different from that obtained in a 
single film, exemplified by the line of 
slope \. 

The television receiver may be com- 
plicated somewhat by making the trans- 
mittance proportional to some power, 
n, of the signal voltage. That is, 

(5) 



where 



Then: 



T = 



.S = signal voltage, 
k 3 = a constant. 



R 



ry* 4 



(6) 
(7) 
(8) 
(9) 



where : 



Most actual television receivers follow a 
law in which n has some value between 2 
and 3. The plots of relative R for these 
values, assuming in each case k as 
equal to 1, are indicated in Fig. 7. 
They represent a slightly better fit than 
for n = 1, only, however, in that the 
general slope tends to be somewhat 
closer to J. 

Schade points out, furthermore, that 
actual motion picture film, as projected 
on a screen, is more complicated than a 
single emulsion. It consists of a nega- 
tive printed on a positive, which is 
projected through an optical system. 
The emulsion having the greater graini- 
ness is usually the negative, because the 



102 



August 1951 Journal of the SMPTE Vol. 57 



stakes in higher film speed (and conse- 
quently greater graininess) are more im- 
portant for the negative than for the 
print. The negative graininess is printed 
on the positive with an inverse den- 
sity scale (i.e., black turns to white, 
and vice versa). The graininess con- 
tribution of the negative is further 
changed by the gamma of the positive 
emulsion and by a small amount of 
blurring in the printing process. Fin- 
ally, the graininess of the positive print is 
somewhat reduced in projection by the 
small amount of blurring in the optical 
projection process. Schade goes through 
estimates of all these effects, and finally 
ends with a deviation ratio, R, as a func- 
tion of the equivalent density, D, or 
transmittance, T, of the picture as 
projected on the screen. This is plotted 
in a somewhat modified form, as the 
curve for n = 1 in Fig. 8. The modi- 
fication is obtained from a transforma- 
tion of equation (8) by placing: 



Then, 



(10) 



The curve for n = I then represents 
AS as a function of T for k$ and , each 
equal to 1. In a simple transmission 
system having a receiver characteristic 
for which n 1 , the quantity A6 1 , repre- 
senting the rms value of the superposed 
noise, would be independent of the in- 
stantaneous magnitude of the signal or of 
its corresponding screen luminance, and 
would thus be represented as a constant 
in Fig. 8. The curve, however, shows 
how it must vary with the relative screen 
luminance to correspond with the effect 
obtained from the composite photo- 
graphic graininess as deduced by Schade. 

To show the effect of taking account of 
the negative graininess and the other 
factors, the fine-dotted curve marked 
"positive only" in Fig. 8 is a reproduc- 
tion, in the transformed coordinates, of 
the straight line for fine-grain film of 
Fig. 6. The blurring effects more than 
compensate for the graininess contribu- 



tion from the negative, in the very ex- 
treme highlights, where the equivalent 
noise of the positive graininess alone 
comes out greater than for the composite 
effect. 

The curves have also been plotted 
showing the equivalent noise, AS, for a 
simple transmission system where the re- 
ceiver characteristic has the more usual 
exponents n = 2 and 3. For these the 
equivalent noise is much more nearly 
constant than for n = 1. Nevertheless, 
it does show a range of equivalence, 
which indicates that the incidence of 
photographic graininess is not wholly the 
same as that of additive random noise. 

In an actual receiving tube the ex- 
ponent, n, is approximately constant 
only over a range of luminances, and 
drops deeply toward the lowest lumi- 
nances used. The equivalence in Fig. 8, 
therefore, departs even further than sug- 
gested, for the very low transmittances. 

The equivalence which is of greatest 
significance is, of course, that which 
occurs in the transmittance region of the 
picture where the noise is most visible. 
Unfortunately, this is not too well 
known at the present time. However, in 
the same communication, Schade pre- 
sents the results of some threshold 
measurements of random noise as a func- 
tion of the picture luminance where the 
noise is perceived. A replot of his 
curve, for noise perceived on picture 
modulated fields, is shown in Fig. 9, 
translated into the same coordinates as 
Fig. 8. His curve has been translated 
to 15 ft-L equal 100% transmittance. 

The fact that the curves run below 
those for the same indices in Fig. 8, in 
some part of the transmittance range, 
indicates that the photographic graini- 
ness for which Fig. 8 is plotted will be 
above threshold for those transmittances. 
This is consistent with the statements 
which have been made before. The 
margin runs in the order of 5 db and is 
at its maximum in the transmittance 
region between 0.15 and 0.3. If a con- 
stant additive noise were superposed, of a 



Pierre Mertz: Random Noise 



103 



10 



10 



10" 



10" 



n =i 



.001 .01 .1 .2 

RELATIVE TRANSMITTANCE, T 
Fig. 9. Threshold noise variation with transmittance. 



.6 .8 I 



value indicated at the point of maximum 
margin of visibility over threshold, it 
would appear worse than the graininess 
portrayed in Fig. 8, because the margin 
of visibility over threshold would be 
greater in the lower transmittances. To 
obtain a constant additive noise showing 
about the same picture impairment as 
the photographic graininess, the margin 
of visibility of the latter has been trans- 
lated to the region of greatest suscepti- 
bility, i.e., in Fig. 9, of lowest transmit- 
tance, which has arbitrarily been taken 
as 0.01 . (There might be some question 
as to whether, in consequence of the re- 
marks made regarding Fig. 8, this is not 
too low for validity in actual receivers.) 
Under these conditions the noise equiv- 
alences are (measured to the signal at 
100% transmittance): 



n = \ 55 db 

2 42 

3 38. 

These are indicated by the tips of the 
arrows at the left end of the curves in 
Fig. 8. The figures need further correc- 
tions as follows: 

+2.5 db ratio of effective apertures (44/j 

diam to 1 . 32 mils 2 ) 
1 . ratio of frame rates 

+ 2.5 addition of synchronizing pulse 
+2.9 frequency weighting 

6.9 net 
say, +7 (rounded) 

Thus, the figures above deduced are 
changed to: 

n = 1 62 db 

2 49 

3 45. 



104 



August 1951 Journal of the SMPTE Vol. 57 



These figures, ignoring the case for 
n = 1, are slightly more lenient than, 
but in substantial agreement with, those 
derived from sound-track data. They 
are somewhat suspect for two reasons. 
First, the aperture data imply a poorer 
projected-film picture than television 
picture, which does not appear wholly 
reasonable. In the second place, the 
random noise is shown to be first per- 
ceived in the extreme blacks, which is 
contrary to general observation. This is 
caused by the trend of the curves in 
Fig. 9, which does not show the usual 
rise of threshold noise to a constant to- 
ward low luminances, which again is the 
indication of deviation from the Weber- 
Fechner law. 

In a general way, it can be said that 
while the discussion of the detailed 
points has clarified our understanding of 
the relationship between photographic 
graininess and random noise, it has not 
seriously changed the conclusions from 
the simple sound-track deductions. 

Schade has also compared the inci- 
dence of noise in the image orthicon 
camera with that of photographic grain- 
iness. This correlates somewhat more 
closely than that of the additive noise in 
the simple circuit. Computing this 
noise to threshold leads to a requirement 
of 45 db to the maximum picture signal. 
This is corrected to 42 db by the change 
from 4 to 8 me (i.e., without the change 
of observer viewing distance involved in 
the proposal which has been made 
above). By allotting a contribution of 6 
db below this to "video amplifiers or 
signal distribution systems," the figure of 
48 db is reached. To allow for super- 
position of the synchronizing signal, 2.5 
db should be added to this and for con- 
version to weighted noise, 5.6 db should 
be added to the 8-mc figure, and 2.9 db 
to the 4-mc figure. Both, then, lead to 
50-db weighted noise overall, and 56 db 
allocated to the electrical transmission. 
This allocation has not been made in 
any of the other figures presented, which 
merely deal with overall requirements. 



5. Noise Data on Pickup Equipment 

Some modern television pickup tubes 
have been described recently in the RCA 
Review, 9 and their signal-to-noise ratios 
are estimated under reasonably typical 
lighting conditions as adapted to their 
respective uses. 

The 1850A iconoscope (photocathode 
image area, 17 sq in.) is estimated to 
have an unweighted signal-to-noise ratio 
of 35.6 db. With synchronizing pulse, 
this becomes 38 -j- db. This is a 
"peaked" or "uptilted" noise, and the 
equivalent flat noise is estimated in the 
paper at 45.1 db (with synchronizing 
pulse 48 db). The allowance for the 
"uptilted" over the flat noise is, there- 
fore, assumed at 9 to 10 db, compared 
with the 3.4 db which has been deduced 
above. This discrepancy in weighting 
has already been noted. Using the 
weighting of Fig. 2, the weighted figure 
would be 44 -f- db (with synchroniza- 
tion). 

The 1848 iconoscope (photocathode 
image area, 6 sq in.) is estimated as 
having an unweighted signal-to-noise 
ratio of 29.8 db (with synchronizing 
pulse 32 db). This noise is character- 
ized as "not always acceptable." The 
noise is also "peaked," and, using the 
weighting of Fig. 2, the figure would be 
39 - db. 

The 2P23 image orthicon (photo- 
cathode image area, 1.23 sq in.) is 
estimated as having, with the original 
gun design, an unweighted signal-to- 
noise ratio of 28 db (with synchronizing 
pulse 30 + db). With a new gun design 
this was raised to 30.9 db (with syn- 
chronizing pulse 33 + db). This is a 
"flat" noise, and no extra allowance is 
due. However, weighted noise (with 
the weighting of Fig. 2) would be 36 + 
db. The performance from the stand- 
point of noise is characterized in the 
paper by the statement, "Although this 
value is on the low side, it is acceptable 
for outside pickups." 

The 5655 image orthicon (photo- 
cathode image area, 1.23 sq in.) is 



Pierre Mertz: Random Noise 



105 



Table III 



Distribution 




Flat 


Uptilted 


Sharp cutoff to 4 me 






Integrated, unweighted power 





-4.77* db 


Unweighted /weighted power, curve I 


2.87 


6.34 


Unweighted /weighted power, curve II 


1.66 


3.30 


Unweighted /weigh ted power, curve III 


0.90 


1.60 


Sharp cutoff to 8 me 






Integrated, unweighted power 


3.00 


4.26* db 


Unweighted /weigh ted power, curve I 


5.64 


12.72 


Unweighted /weighted power, curve II 


4.21 


9.56 


Unweighted /weighted power, curve III 


2.87 


6.35 


Sloping cutoff to 5 me** 


Flat 


"Coaxial"** 


Unweighted /weighted power, curve I 


2.2 


6.9 db 



* In this distribution the watts per kilocycle have been set as equal at 4 me to the watts per 
kilocycle in the flat distribution. 
** See reference 1. 



estimated as having an unweighted 
signal-to-noise ratio of 38.1 db (with 
synchronizing pulse 41 db). This is 
flat, so that with the weighting of Fig. 2, 
the weighted figure would be 43.5 db. 
Compared with the 2P23 tube, the 
performance is characterized, "This gain 
in signal-to-noise ratio is very worth 
while and makes the tubes acceptable 
for studio application." It is under- 
stood, informally, that for good tubes the 
figure of 38.1 db is likely to rise to a 
little over 40 db. 

The 5769 image orthicon (same size of 
photocathode image as 2P23 and 5655) 
is described, but no figures given on 
signal-to-noise ratio except the state- 
ment, "The 5655, however, is superior 
in its signal-to-noise ratio. ..." 

The 5820 image orthicon (same size of 
photocathode image as others) is de- 
scribed in the more recent paper of the 
reference, but no statement is made as 
to its signal-to-noise performance. It is 
understood, informally, that its un- 
weighted signal-to-noise ratio is of the 
order of 34 db. Weighted, and with 
synchronizing pulse, the figure would 
become 40 db. 

No data are given in this literature on 



the signal-to-noise ratio of the 5826 
image orthicon (same size of photo- 
cathode image as others), but it is under- 
stood, informally, to be of the order of 37 
or 38 db. Weighted, and with syn- 
chronizing pulse, this becomes 43 db. 

It has been noted above, in the presen- 
tation of Fig. 1, that the dotted lines 
refer to the data as taken. In the tests 
the slide was scanned by a special test 
scanner, revised from a prewar scanner. 10 
From general experience with this scan- 
ner, it is considered to have low though 
visible noise. By the addition of a con- 
stant noise, on an rss basis, to that 
indicated by the dotted lines, they can be 
straightened out, as shown by the solid 
lines, and it is estimated that this con- 
stant noise measures the contribution of 
the film scanner. The figure is shown 
to be 46 db signal-to-weighted noise 
(including synchronizing signal). If the 
distribution were flat, the unweighted 
figure, for the 4-mc band, would be 43 4- 
db. 

6. Appendix 

For simple reference the results of 
computations of two sharp cutoff and 
two sloping cutoff distributions, with the 



106 



August 1951 Journal of the SMPTE Vol.57 



weightings shown in Fig. 2, are given in 
Table III. 

References 

1. P. Mertz, "Perception of television 
random noise," Jour. SMPTE, vol. 54, 
pp. 8-34, Jan. 1950. 

2. M. Luckiesh and F. K. Moss, "The 
variation in visual acuity with fixation- 
distance," /. Optical Soc. Am., vol. 31, 
pp. 594-595, Sept. 1941 ; The Science of 
Seeing, Van Nostrand, New York, 1937; 
"The dependency of visual acuity upon 
stimulus distance," /. Optical Soc. Am., 
vol. 23, pp. 25-29, Jan. 1933. 

E. Freeman, "Anomalies of visual 
acuity in relation to stimulus-dis- 
tance," /. Optical Soc. Am., vol. 22, pp. 
285-292, May 1932. 

3. P. Mertz, A. D. Fowler and H. N. 
Christopher, "Quality rating of tele- 
vision images," Proc. Inst. Radio Engrs., 
vol. 38, pp. 1269-1283, Nov. 1950. 

4. G. E. K. Mees, The Theory of the 
Photographic Process, Macmillan, New 
York, 1942. 

5. O. H. Schade, "Electro-optical charac- 
teristics of television systems : Introduc- 
tion," RCA Rev., vol. 9, no. 1, pp. 5-13 
Mar. 1948. 

"Part I Characteristics of vision and 
visual systems," ibid., pp. 13-37, Mar. 
1948. 

"Part II Electro-optical specifica- 
tions for television systems," ibid., no. 2, 
pp. 245-286, June 1948. 
"Part III Electro-optical character- 
istics of camera systems," ibid., no. 3, 
pp. 490-530, Sept. 1948. 
"Part IV Correlation and evaluation 
of electro-optical characteristics of 
imaging systems," ibid., no. 4, pp. 653- 
686, Dec. 1948. 

"Image gradation, graininess and 
sharpness in television and motion pic- 
ture systems," Part I : Image structure 
and transfer characteristics," Jour. 
SMPTE, vol. 56, pp. 137-177, Feb. 
1951. 

6. H. L. Logan, "Brightness and illumi- 
nation requirements," Jour. SMPE, 
vol. 51, pp. 1-12, July 1948. 

7. M. W. Baldwin, "Allocation standards 
for very high-frequency television and 
frequency modulation broadcasting," 



(Report of experiments of T. R. D. 
Collins, Annex 8) Proc. Joint Technical 
Advisory Comm., vol. II, Dec. 1948. 
(This publication is available at The 
Joint Technical Advisory Committee, 
1 East 79th St., New York 21.) 
E. W. Chapin and G. H. Brown, Ex- 
hibits 389 and 424, respectively, 
Dockets 8736, 8975, 9175 and 8976, 
"Record of FCC Hearing on Color 
and Allocations, 1950." (This pub- 
lication is available at the Federal 
Communications Commission, Wash- 
ington, D.C.) 

8. L. A. Jones and G. C. Higgins, 
"Photographic granularity and graini- 
ness, 

"Part I The relationship between the 
granularity and graininess of de- 
veloped photographic materials," /. 
Optical Soc. Am., vol. 35, pp. 435-457, 
July 1945. 

"Part II The effects of variations in 
instrumental and analytical tech- 
niques," ibid., vol. 36, pp. 203-227, 
Apr. 1946. 

"Part III Some characteristics of the 
visual system of importance in the 
evaluation of graininess and granu- 
larity," ibid., vol. 37, pp. 217-263, 
Apr. 1947. 

"Part IV Visual acuity thresholds; 
dynamic versus static assumptions," 
ibid., vol. 38, pp. 398-405, Apr. 1948. 
"Part V A variable-magnification 
instrument for measuring graininess," 
ibid., vol. 41, pp. 41-52, Jan. 1951. 
"Part VI Performance character- 
istics of the variable -magnification 
graininess instrument," ibid., vol. 41, 
pp. 64-75, Feb. 1951. 
"Part VII A microphotometer for 
the measurement of granularity," 
ibid., vol. 41, pp. 192-200, Mar. 1951. 
9. R. B. Janes, R. E. Johnson and R. S. 
Moore, "Development and perform- 
ance of television camera tubes," RCA 
Rev., vol. 10, pp. 191-223, June 1949; 
R. B. Janes, R. E. Johnson and R. R. 
Handel, "A new image orthicon," 
ibid., vol. 10, pp. 586-592, Dec. 1949. 
10. A. G. Jensen, "Film scanner for use in 
television transmission tests," Proc. 
Inst. Radio Engrs., vol. 29, pp. 243-249, 
May 1941. 



Pierre Mertz: Random Noise 



107 



Modified Negative Perforation 

Proposed as a Single Standard for 35-Mm 
Negative and Positive Motion Picture Film 



By W. G. HILL 



The existence of two or more perforation shapes for 35-mm films has, for many 
years, been considered undesirable. For processes requiring accurate film 
positioning, the dual Standard of Negative perforation for camera stock and 
Positive perforation for release stock does not suffice. Registration problems 
are minimized if Negative perforations are used throughout; experience, 
however, has shown that projection life is short. The Modified Negative 
perforation, with fillets at the corners, has improved resistance to tear while 
preserving the general negative form corresponding to conventional piloting 
means. Tests conducted show that better film positioning is accomplished in 
conventional camera and printing equipment for film with Modified Negative 
perforations than for film with Dubray-Howell perforations. The method of 
evaluating film location during exposure and printing is described and evi- 
dence of results presented. Photoelectrically recorded charts show the extent 
of out-of-register which resulted for various combinations of perforation types. 
Film-life projection tests indicate that the Modified Negative perforation is 
equal or superior to the Dubray-Howell perforation. 



-L HE PERFORATED HOLES in motion printing and projection equipment 

picture film provide a means whereby whereas pilot-pin devices are more com- 

the continuous strip material can be mon in cameras and step printers where 

propelled in synchronism with and in the advance of the film is intermittent 

register to various machine components and extreme accuracy is required. For 

used in the production and reproduction many processes, such as in color film 

of successive picture images. For the work, consistently accurate positioning of 

most part, sprocket wheels and pilot pins the film is of utmost importance. This 

are used to engage the film perforations is particularly true when more than one 

and effect positioning of the film strip. negative film is used to make up the 

The former are most extensively used in master, and is desirable in all reproduc- 
tion processes in order to preserve screen 

A paper presented on May 2, 1951, at the steadiness. The fit of the perforations 

W^SlSo Divisit, JM&bZ n < he ^^ion sprocket teeth or pi.ot 

& Film Corp., Binghamton, N.Y. pins influences the degree of steadiness 

108 August 1951 Journal of the SMPTE Vol.57 



in the final release print and is, therefore, 
of vital concern to the motion picture 
industry. 

The general form of the Standard 
Negative perforation, modified to the 
extent of incorporating slight fillets at 
the corners, is a shape of perforation 
worth considering as a single standard 
for 35-mm film. Experience with the 
negative form and tests conducted on 
film with the suggested modified per- 
forations show this curved-end type of 
hole to be suitable for camera, dupe and 
release films. Image registration and 
picture steadiness, as produced with 
typical equipment, are improved when 
using the Modified Negative perforations 
noted above over that accomplished with 
the use of the present Negative and Posi- 
tive combination or proposed rectangular 
Dubray-Howell perforation. Tearing of 
the film at the perforation during projec- 
tion is less severe for the Modified Nega- 
tive perforations than for the Dubray- 
Howell perforations tested. It appears 
that advantages gained by adopting the 
Modified Negative perforation as a single 
standard can be realized without the 
necessity of altering equipment. 

Perforation Shape 

Considerable information dealing pri- 
marily with the size and shape of the hole 
has been published on the standardiza- 
tion of perforations for 35-mm films. 
The history and reference to papers on 
the subject are well covered in a Journal 
report. 1 The proposal embodied in the 
report and presented for trial and com- 
ment specifies a rectangular perforation 
0.110 in. X 0.073 in. with 0.013-in. 
corner fillets. This form of perforation 
was proposed by Dubray and Howell in 
1932 and is usually referred to as the 
Dubray-Howell perforation. With re- 
cent acceptance of this perforation by 
some processing companies, we now face 
the problem of dealing with three types 
of perforations instead of two, which the 
industry has accepted as standards for 
many years. The Dubray-Howell per- 



foration is substantially the same shape 
as the Standard Positive, but has a 
height of 0.073 in. instead of 0.078 in. 
and corner radii of 0.013 in. as against 
0.020 in. for the Positive. The 0.073-in. 
dimension (same as for the Standard 
Negative perforation) is calculated to 
give no new difficulties in sprocket- 
tooth-to-film interferences. More im- 
portant is the fact that there are ad- 
vantages in the overall perforation size 
being the same for all camera, dupe and 
printing stocks. It is believed that 
with the new low-shrink safety film sup- 
ports there is no valid reason to continue 
using the oversize Positive perforation. 
Experience has shown that the smaller 
perforations of like size and shape can be 
successfully used for all general types of 
35-mm film. Since most commercial 
film-handling equipment, precision built 
to provide accurate registration, is de- 
signed to fit the Standard Negative per- 
foration, Z22.34, it appears advisable to 
maintain the overall size therein specified 
for negative raw stock rather than the 
larger positive size. 

The circular-end form, like the Nega- 
tive standard which has been almost 
universally used since 1918, gained wide 
acceptance and is still used for work re- 
quiring accurate registration. Although 
efforts have been made in this country 
and Europe to standardize on the rec- 
tangular Positive perforation, and more 
recently in this country to standardize 
on the Dubray-Howell perforation, the 
round-ended perforation has, neverthe- 
less, survived. Reluctance to accept the 
Dubray-Howell type of perforation as a 
single standard may be explained par- 
tially by the fact that new pins and 
sprockets to correspond are necessary in 
order to gain the most benefits in im- 
proved registration. In this connection, 
it should be noted that in the report of the 
Subcommittee on Perforation Standards, 
published in the Journal^ reference is 
made to proposed new pilot pins and 
sprocket teeth to fit the Dubray-Howell 
perforation for improved means of regis- 



W. G. Hill: Modified Negative Perforation 



109 







}- y/o *-J U .//o J I - .//o J 

Fig. 1. Relationship of various perforations to pilot pins and sprocket teeth. 



tration. In regard to printer sprockets, 
the report points out that, "... the 
recommended modification of printer 
sprocket design would be a marked im- 
provement in the printing process, but 
would not be essential." Further, the 
report states, "It is to be noted, however, 
that locating on the unmodified printer 
sprocket two films having rectangular 
perforations requires some care." Stock 
films with Negative perforation could 
not, of course, be accommodated on rec- 
tangular teeth of the proposed modified 
sprocket. Because of such complica- 
tions and additional expense of change- 
overs, the rectangular perforation form 
has not been accepted by the industry as 
the single standard for negative and posi- 
tive films. The negative Bell & Howell 
perforation without corner fillets, al- 
though proven by experience to register 
accurately on existing equipment and 



provide adequate steadiness, is not 
ideally suited for projection films because 
of its low resistance to tear. The solu- 
tion seems to be the establishment of a 
single universal perforation which will 
give good registrations on present piloting 
pins and sprockets and at the same time 
have sufficient strength so as not to limit 
projection life. Further, such a per- 
foration should, when used for positive 
and negative film or in conjunction with 
"stock" film having Standard Negative 
perforations, register with the best 
possible accuracy without the necessity of 
altering equipment. The author be- 
lieves that a modified form of the 
Standard Negative perforation, discussed 
in this paper, meets these requirements 
and makes possible the unlimited use of 
form-fitting sprockets for side guiding. 

Figure 1 shows four types of perfora- 
tions under consideration and the rela- 



110 



August 1951 Journal of the SMPTE Vol. 57 



D-H PERR TO 
NEW TOOTH 



MOD. NEC. PERF. 
TO NEW TOOTH 



D-H PERF. TO 
WORN TOOTH 




Fig. 2. Drawing showing side clearance between 
perforation and guiding sprocket. 



tion each may assume with respect to 
commonly used pins and sprocket teeth. 
The curved-end form, Negative and 
Modified Negative, the latter differing 
from the Standard Negative only in the 
0.010-in. fillet at the corners, are sub- 
stantially full fitting with the pilot pins. 
In contrast to this, the rectangular Du- 
bray-Howell and Positive perforations 
locate at the ends by point contact only. 
The Positive hole, being 0.005 in. higher 
than the pin thickness, does not, of 
course, fit along both long sides as do the 
other three holes. As for the relation 
with typical printer sprocket teeth, the 
round-ended forms locate sidewise at the 
driving tooth, whereas clearance exists at 
the short sides of the Dubray-Howell and 
Positive holes. In the case of the projec- 
tor sprocket and those used where regis- 
tration is not critical, the relation of per- 
foration to tooth is similar for all types 
shown. The fit of perforations to the 
registering sprocket tooth as shown for 
printers suggests that the same tooth 
form could be used in projectors and re- 
lated equipment where better steadiness 
is desirable. Note that the round-ended 
form of hole, with tooth to correspond, 
provides what appears to be a more 
reliable self-centering means. If wear on 



the sprocket tooth is considered, it is 
evident that the round-ended form is 
superior in that, as the face and the side 
of the tooth wear, the Negative form 
tends to wedge and center the perfora- 
tion. The rectangular tooth, when 
worn, is not self-compensating and clear- 
ance at the sides will result. This is 
shown schematically in Fig. 2. Wear on 
the sides of the rectangular form results in 
clearance between tooth and perforation 
and destroys the ability of the tooth to 
register the film properly. A similar 
condition may result for pilot-pin regis- 
tration. Guiding the film by full-fitting 
pins or teeth at one row of perforations is 
common practice where positioning of 
the film is critical. But where side mo- 
tion need not be closely controlled, the 
teeth are narrower than the perforation 
width. In this case, shoulder edge 
guides are usually used and for such 
applications the perforation shape does 
not pose a problem. As for affecting 
accurate transverse registration by forc- 
ing the film against one side of the tooth, 
those familiar with film-handling equip- 
ment recognize the potential difficulties. 
It appears evident, therefore, that the 
adoption of the suggested Modified 
Negative perforation should be given 



W. G. Hill: Modified Negative Perforation 



111 



consideration. Little, if any, reluctance 
to accepting such a perforation is ex- 
pected if field trials bear out our finding 
as determined by factory tests. A 
single-perforation type would permit 
reduction of tool expense and inven- 
tories for the film manufacturers, and 
would permit greater flexibility in 
machine usage. The expense of chang- 
ing to the specific Modified Negative 
form suggested would be no greater than 
for the Dubray-Howell. In fact, when 
considering the possible necessity of 
changing equipment which is now de- 
signed to register Standard Negative 
perforations, the expense for the change 
to Dubray-Howell would be greater. 
For the studio and laboratory, no extra 
expense or new problems should arise by 
the acceptance of the Modified Negative 
perforation. There would be no need to 
provide two types of pins or heads. 
With all new films supplied with Modi- 
fied Negative perforations, the registra- 
tion problem, particularly if stock nega- 
tives must be used, is simplified. For the 
film distributors and theaters, the Modi- 
fied Negative perforation should give 
sufficient resistance to tear at the per- 
foration area. Indications are that the 
Modified Negative hole weakens the film 
less than the Standard Negative and is 
equal to or better than the Dubray- 
Howell. 

Briefly, the Modified Negative type of 
perforation has several advantages over 
the Dubray-Howell form. The most 
outstanding, perhaps, is the improve- 
ment gained in registration on standard 
continuous printers which are used ex- 
tensively for making final release prints. 
Also important is the fact that existing 
perforated film could be run on any 
equipment made to conform specifically 
to the Modified Negative perforation. 

The discussion to follow describes 
actual tests with camera and printing 
films having various types of perfora- 
tions. The method of evaluating "un- 
steadiness" is indicated and evidence of 
the results presented in the form of re- 



corded charts. Tear studies comparing 
the Dubray-Howell and the Modified 
Negative perforation are also described. 

Test Method Film Registration 

The term registration, when used in 
connection with motion picture-making 
processes, generally implies the position- 
ing of one film with respect to others or 
with respect to some fixed part of the 
equipment. Film exposed in the camera 
is piloted by pins engaging the perfora- 
tions so that the film is oriented similarly 
for each successive frame and accurately 
positioned. Print registration is accom- 
plished by piloting the picture negative 
and the duplicating stock accurately 
frame by frame or perforation by per- 
foration, so the image transfer is "in- 
register." Any out-of-register con- 
tributes to picture unsteadiness and, for 
processes requiring multiple exposures, 
causes poor image definition. 

The perforated holes are punched in 
the film by tools made to extremely close 
tolerances. These holes serve as a refer- 
ence point to which image position is 
gaged. The degree of improper regis- 
tration and variations in film positioning, 
therefore, can be determined by measur- 
ing the distances from the perforations to 
a point in the photographic image. The 
process of frame-by-frame measuring of 
these distances under the microscope is 
laborious and, consequently, is usually 
limited to comparatively short samples. 
To check the practical significance of 
such findings, it is desirable to examine 
longer lengths of film and correlate the 
data with results as found by a jury 
viewing the projected picture. The 
method of evaluating steadiness used by 
Ansco in the studies described here per- 
mits visual examination of the projected 
image and, at the same time, records the 
extent of image shift attributed to im- 
proper piloting of the film at the time of 
exposure. Long lengths of film can 
thereby be tested and data obtained 
without the need of the time-consuming 
frame-by-frame measurements. The sys- 



112 



August 1951 Journal of the SMPTE Vol. 57 





COMPOSITE OF A8, B 



,\ 



TEST PATTERN B PRINT OF COMPOSITE 



\ 



Fig. 3. Target patterns. 

tern of using double-exposed images to 
indicate out-of-register, which is familiar 
to some, was selected not only to enable 
convenient viewing by projection but 
also to permit the use of a single-channel 
recording device. 

Two "targets," illustrated in Fig. 3, 
were provided in order that exposure, 
first to one and then to the other, would 
result in cross-line patterns and also form 
"light slits," the sizes of which vary 
depending on the differences in position- 
ing of the film during the first and second 
exposure. The crossover lines, forming 
tapered wedges, are used primarily for 
visual studies of the projected image, 
whereas the stepped slits are arranged 
conveniently for photoelectric recording 
of the vertical and horizontal variations. 
Figure 4 represents the composite formed 
by superimposing image of target A and 
target B, shown in Fig. 3. The size of 
the original target was selected so as to 
give successive step distances of 0.002 in. 



Fig. 4. Composite of target patterns. 

on the wedge image formed on the cam- 
era film. This provided a means of 
visual checking of the approximate 
variations in "slit" width on the printed 
film during projection. The system of 
superimposing images described is appli- 
cable not only to testing registration 
ability of equipment for a particular 
film, but valuable, as in this case, in 
evaluating different films or types of per- 
foration holes on given equipment. In 
the latter case, the same camera, printer 
and related apparatus were used for all 
comparison tests, thereby eliminating 
variables in equipment. It is well to 
point out that in testing for registration, 
by the method of superimposing films, 
the maximum shift of the first to second 
images may be twice that for either image 
separately. This total shift of one with 
respect to the other, however, is what 
may be encountered in actual picture 
making and consequently is indicative of 
the true situation. 



W. G. Hill: Modified Negative Perforation 



113 



For purposes of investigation. 300 ft of 
each test film were exposed in a camera; 
100 ft to target A; the second 100 ft to 
target B; and the third 100 ft, consecu- 
tively superimposed to targets A and B. 
The latter, composite negative of A and 
B, was used to check registration in the 
camera. For the print tests, a 100-ft 
dupe film was printed from camera nega- 
tive of target A and then "in-register" 
with the negative of target B. Prints of 
the resulting picture composites (illus- 
trated in Fig. 4) were projected and 
image registration of the various samples 
compared. In judging image move- 
ment, that due to out-of-register in the 
camera, of course, was taken into ac- 
count. Picture unsteadiness of the pro- 
jected step-wedge images was recorded 
by means of a photocell and appropriate 
electrical circuits, a detailed description 
of which is given in the paper by R. W. 
Lavender, immediately following in this 
JOURNAL. 

Test Apparatus and Equipment 

Photographic apparatus used in the 
testing program was standard commer- 
cial equipment, typical of that in general 
use by the trade. No attempt was made 
to replace critical parts of the equipment 
which might have been worn by normal 
use. On the contrary, equipment used 
for routine trials was selected as being 
equivalent to that in operation in many 
studios and laboratories. Pilot pins and 
registering sprockets were the Standard 
Negative type. Most of the trials were 
made at the Ansco factory; however, 
some runs were conducted at other 
plants. Although it is recognized that 
the introduction of a new perforation 
standard would affect operations on a 
number of different machines including 
special-effects projectors, splicers, re- 
corders, etc., it was deemed sufficient to 
limit the tests to typical cameras, con- 
tinuous printers, step-optical printers and 
theater projectors. Film advance and 
registration mechanisms contained in 



such units represent, in general, the 
types of movements universally used. 
Therefore, evaluation of steadiness and 
performance for the test described here 
was limited to trials on the four types of 
equipment noted. 

A Mitchell camera having synchro- 
nous motor drive and Standard Negative 
pulldown and pilot pins was used. The 
Bell & Howell model continuous printer, 
used for making evaluation prints, had 
Negative-type sprocket teeth for effecting 
side guiding of Standard Negative per- 
forations. Step-optical prints were run 
on an Acme-Dunn unit which is main- 
tained by our Motion Picture Develop- 
ment Department for testing purposes. 
Projection runs were made on a Super 
Simplex with a 0.935-in. diam, 16-tooth, 
intermittent sprocket. The 50-amp arc 
light was used during wear and tear tests. 
For steadiness evaluation trials, however, 
the light was converted to a 2100-w, 60-v 
incandescent lamp. This light source 
provided constant illumination which is 
essential to the system used for recording. 

Figures 5 A, 5B and 5G show the test 
screen and equipment setup for record- 
ing steadiness data. View 5A is of the 
projection side of the screen on which is 
mounted two photocells and the calibrat- 
ing unit. The photocells are arranged 
so the projected image of the step-wedge 
formed on the film by the double- 
exposed target pattern falls on the 
light-sensitive cell element. View 5B 
is of the calibrating device. This is 
simply a d-c motor which drives an 
eccentric bushing mounted to form a 
rectangular window with a second bush- 
ing and the top and bottom of the open- 
ing in the cell housing. Both bushings 
are made to push-fit over the shafts in 
order that different diameters and eccen- 
trics may be used to vary the slot width. 
Figure 5G shows the amplifier and re- 
cording equipment mounted at the 
rear of the screen. The test screen 
was positioned so as to give a SOX 
enlargement of the projected image at 
the screen. 



114 



August 1951 Journal of the SMPTE Vol.57 





Fig. 5A. Test screen from projector 
side, showing photocell holders and cali- 
brating unit. 



Fig. 5B. Close-up of calibrating unit 

mounted in front of photocell. 




Fig. 5C. Electronic units and recorder mounted at rear of screen. 



Registration Studies 

Each test series, including samples of 
various perforations under consideration, 
was conducted on material from the same 
film coating and, where possible, was 
selected from the same 35-mm roll. For 
the most part, testing was limited to 
safety base materials typical of those now 
used in motion picture work. Some 
steadiness checks, however, were made on 



nitrate base but no attempt was made to 
draw comparisons between performance 
of the two materials. Dubray-Howell 
and Modified Negative tools, used in 
perforating the sample films for test X, 
were made to like tolerances and e ected 
to give comparable hole sizes. All runs 
in a given series were made consecu- 
tively under similar conditions so as lo 
eliminate variables which might reflect 



W. G. Hill: Modified Negative Perforation 



115 



FILM REGISTRATION IN PRINTER 

PHOTO-ELECTRIC RECORD OF PROJECTED IMAGE 



SIDE MOTION 



STD. NEC. TO MOD. NEC. 



STQ NEC. TO D-H. 




STD. NEC. TOD.-H. REPROJECTION I 






CALIBRATION 
Dlv. s .OOO2" 



Fig. 6. Charts Test X on sprocket printer. 



in the data and thereby render the com- 
parisons questionable. 

The steadiness or degree of film regis- 
tration accomplished on a Bell & Howell 
continuous printer, test X, is indicated in 
Fig. 6. These charts are the results of 
photoelectrical detection of the relative 
shift of first- and second-exposure images 
as observed during projection of the 
printed test film. The pattern, forming 
light slits at which the variations were 
measured, was the result of printing the 
negative of target A to the positive film 
and then printing the negative of target 
B to the same positive film. Therefore, 
variations or out-of-register shown are 



those due to nonuniform positioning of 
the films on the printing sprocket and in- 
accuracies in the original negatives. 
The latter are comparatively small as 
will be shown later in Fig. 8. Film 
having Standard Negative perforations 
was double printed to films with Modi 
fied Negative, Standard Positive and 
Dubray-Howell perforation. The re- 
corded out-of-register results are shown 
by charts 1, 3 and 5 of Fig. 6. In the 
case of chart 1, Standard Negative to 
Modified Negative, the average side 
motion was approximately 0.0007 in. 
For chart 3, to Standard Positive, the 
variation is in the order of 3 times that 



116 



August 1951 Journal of the SMPTE Vol. 57 



FILM REGISTRATION IN PRINTER 

PHOTO-ELECTRIC RECORD OP PROJECTED IMAGE 



SIDE MOTION 



VERTICAL 




Fig. 7. Charts Test X on optical printer. 



for chart 1, and for chart 5, to Dubray- 
Howell, about 4 times. The results of 
printing camera negatives, having Modi- 
fied Negative holes, to films with the 
same type of perforations, and negatives 
with Dubray-Howell holes to like film, 
are shown by charts 2 and 4, Fig. 6. 
Variations for the Modified Negative 
perforation appear to be distinctly less 
than for the Dubray-Howell combina- 
tion. In order to verify the accuracy of 
recording out-of-register, the test print 
was reprojected and the results compared 
with the previous run. One section of 
the chart thus obtained is shown in curve 
6 of Fig. 6. In comparing this with 
curve 5, it will be noted that the duplica- 
tion is near perfect. Vertical motion be- 
tween the first and second printed images 



shown at the right of Fig. 6 appears to be 
comparable for all samples (about 
0.001 in.). The calibration chart at the 
bottom of Fig. 6 was obtained by project- 
ing the clear area of the test film through 
the controlled variable calibrating slot 
and onto the photocell. Knowing the 
magnification and slot-width change at 
the cell, the gain of the unit was set so 
that each small division on the chart 
represented approximately 0.0002 in. at 
the film. With the slot area fixed, and 
the cell receiving light through the clear 
film area, no movement of the recorder 
pen could be detected; thus indicating 
that the variations in light intensity and 
film density were negligible. 

The same camera negatives used for 
the continuous printer test described 



W. G. Hill: Modified Negative Perforation 



117 



FILM REGISTRATION IN CAMERA 



PHOTO-ELECTRIC RECORD OF PROJECTED IMAGE 



SIDE MOTION 



VERTICAL 




Fig. 8. Charts Test X on intermittent camera. 



above were also used for testing out-of- 
register on a step-optical printer. Using 
the same general method as before, the 
charts shown in Fig. 7 were recorded. 
Charts 2, 3 and 4 for Negative-type per- 
forations on originals to Negative and 
Dubray-Howell types are comparable, 
indicating side motion of from 0.0006 to 
0.0008 in. These also show side motion 
to be in the same order of magnitude as 
on chart 1 for the continuous print sam- 
ple of Standard Negative to Modified 
Negative perforations. The print of 
Dubray-Howell to Dubray-Howell, chart 
5, shows greater side movement, from 
0.0010 to 0.0012 in. Vertical motion for 
all step-optical prints was about the 
same (0.0004 in.). The degree of 
vertical unsteadiness in these instances 
was much better than for the continuous 
prints and only slightly worse than for 
the camera test. 



Charts 2, 3 and 4 in Fig. 8 are records 
of variations attributed to inaccuracies in 
positioning of the film in the camera. 
All samples show from 0.0003-in. to 
0.0004-in. variations in the horizontal 
and vertical direction. Chart 1 (Stan- 
dard Negative to Modified Negative) of 
the continuous print sample of least 
variation (0.0007 in. avg.) serves as a 
comparison to the camera registration 
performance curves. 

Test Y, Fig. 9, charts 1, 2 and 3 are 
taken from a different series of camera 
and print film tests. The negative, 
which was perforated with tools con- 
verted from Standard Negative to Modi- 
fied Negative type, was exposed by Ansco 
to test targets as previously described, 
but the printing was done by a commer- 
cial laboratory. These trials served not 
only to verify earlier observations but to 
check the degree of correct registration 



118 



August 1951 Journal of the SMPTE Vol. 57 



FILM REGISTRATION IN PRINTER 



PHOTO-ELECTRIC RECORD OF PROJECTED IMAGE 



SIDE MOTION 




Fig. 9. Charts Test Y on sprocket printer. 



which might be expected when printing 
from the new Modified Negative per- 
forated stock onto stock with the same 
perforations and also onto release or dupe 
film with Positive or Dubray-Howell per- 
forations. The results of this laboratory 
test show the Modified to Modified to be 
best, variations being in the order of 
0.0006 in. For the Modified to Dubray- 
Howell, however, variations were about 
three times greater. It will be noted 
that the calibration amplitude shown by 
the lower chart in Fig. 9 is slightly less 
than for the other figures, the smallest 
scale division equaling 0.0002 in. plus, 
or a little greater than for the other 
figures. This change may be accounted 
for by difference in density of the film 
used for the two series. 

In reviewing steadiness tests con- 
ducted at Ansco over a period of several 
months, it is evident that in each case, 
the curved-end style of Negative or 
Modified Negative perforation is super- 
ior. This form of perforation hole gave 
the best steadiness when used for both 



the camera and print films. Negatives 
printed to film with rectangular per- 
foration were not as good; however, 
they were distinctly better than for the 
Dubray-Howell type perforated camera 
material printed on Dubray-Howell 
perforated release stock. Our findings 
substantiate the theory that improved 
pin registration and sprocket guiding 
will result on commonly used commer- 
cial equipment if film with curved-end 
perforation is used throughout. 

Perforation Wear and Tear Resistance 

Film samples for wear tests were made 
up in 40-ft loops. Although some trials 
were made on loops containing only one 
type of perforation, the data presented 
here is a comparison of two types of 
holes in the same film strip. Both tests 
reported here were on safety film, de- 
veloped clear and projected on the same 
machine. Films for wear tests were not 
waxed or otherwise conditioned to im- 
prove projection life as is usually done 
commercially. In preparing film strips, 



W. G. Hill: Modified Negative Perforation 



119 



Table I. Number of Torn Perforations per Frame 



Film D-145-1 : Loop 1 


Film 


D-145-2: Loop 2 


No. of 
Projections 


Mod. Net?. 
Perf. 


D-H 
Perf. 


No. of 
Projections 


Mod. Neg. 
Perf. 


D-H 
Perf. 


202 
396 
508 
671 
892 
1198 
1273 


2(slight) 
2(1 slight) 
3 
3 
3 
3 
5 


3(slight) 
4(2 slight) 
5(1 severe) 
5 
5 
6 
6 (4 severe) 


220 
321 
715 
974 
1154 
1271 
1628 
1819 
1914 





3(2 slight) 
3 
3 
3 
6(1 slight) 
6(3 severe) 
6 


1(1 slight) 
1 
2(1 slight) 
5 
6(4 slight) 
6(2 slight) 
6 (4 severe) 
6 
6 



half of each length was perforated on a 
machine with Dubray-Howell type tools 
and without cutting the sample, the 
second half was perforated on a machine 
with Modified Negative type tools. 
Films were ink-frame marked for con- 
venience in identifying perforation dur- 
ing the projection run. While wear 
tests were in progress, observations of the 
projected perforation area were made 
and the condition of tearing around the 
perforations noted. 

Film loops were run on a Super Sim- 
plex projector No. 41180, with 50-amp 
arc light and equipped with a 16-tooth, 
0.935-in. diameter intermittent sprocket. 
Table I shows the observed results of 
these projection wear and tear tests on 
two different types of safety base film. 

These and similar tests indicate that, 




LOOP I. 




LOOP I. 



Fig. 10. View of perforation area show- 
ing projection damage to film. 



under normal projection conditions, the 
Modified Negative form of perforation 
weakens the film less than does the 
Dubray-Howell form. 

A study of the types of failure appear- 
ing at the perforation area revealed a 
distinct difference in the cracks which 
were produced during the projection 
runs. Figure 10 shows views of the 
perforation area along one side of the 
Modified Negative and Dubray-Howell 
perforated samples taken at the comple- 
tion of the wear test. It will be noted 
that for the Dubray-Howell type the 
crack is sharp and progresses trans- 
versely. The tear at the corners of the 
Modified Negative hole is broad and 
more in a line forming an angle with the 
straight side of the hole, that is, more 
lengthwise of the film. These breaks at 
the corners of the Modified Negative do 
not extend into the aperture area or to 
the film edge, as do some of the breaks in 
the sample perforated with Dubray- 
Howell holes. Figure 1 1 shows enlarged 
photographs of perforation area from 
loops 1 and 2 after completion of wear 
test runs. Damage to the Dubray- 
Howell perforated sample appears to be 
more severe. In tests conducted for the 
purpose of comparing the Standard 
Negative with Modified and Dubray- 
Howell perforations, the pattern of 
cracks was similar to that shown in Fig. 
10. Although many of the cracks on the 
Standard Negative perforated film were 



120 



August 1951 Journal of the SMPTE Vol. 57 




Loop 1. Film through projector 1273 times. 




Loop 2. Film through projector 1914 times. 

Fig. 11. Photographs of Dubray-Howell and Modified Negative 
perforations at completion of projection wear test. 



D.-H. PERF. 



MOD. NEG PERF 





Fig. 12. Photographs of strain pattern produced by 650-g 
load on perforation edge. 



W. G. Hill: Modified Negative Perforation 



121 



like those shown for the Modified Nega- 
tive, some cracks extended transversley 
much like those on the Dubray-Howell 
perforated sample. These long frac- 
tures which apparently progress across 
the film with repeated loading seem to 
account for the more rapid breakdown. 
In an attempt to determine why the 
two different styles of perforations cause 
film under load to break differently, as 
shown in Fig. 11, strain pattern studies 
were made. Clear safety-base film sam- 
ples, 0.009 in. thick, were supported at 
the perforation edge on a pin 0.070 in. 
wide with 0.01 0-in. corner radii and 
loads of increasing amounts applied to 
the film. By means of polarized light, 
strain patterns were observed. Photo- 
graphs of such patterns are shown in Fig. 
12. Strain areas, indicated by light sec- 
tions, are more sharply defined for the 
Dubray-Howell type hole, the areas of 
strain to no strain for the Modified 
Negative being blended more gradually. 
The strain area for the Modified Nega- 
tive sample extends from the corner along 
the curved end for some distance and 
then gradually falls off; whereas for the 
Dubray-Howell shape, the strain dis- 
appears rather sharply and is not dis- 
tributed as evenly along the short side. 
This, it is believed, explains why the 
break at the corner of the rectangular 
hole progresses across the film and is 
more extensive. 

Conclusions 

The curved-end style of the Standard 
Negative perforation, now almost ex- 
clusively used for camera films, registered 
more accurately in the camera, step- 
optical printer and continuous printer 
than did the rectangular form of Dubray- 
Howell or Standard Positive perforations. 
The Modified Negative perforation with 
0.01 0-in. corner radii compared favor- 
ably to the Standard Negative perfora- 
tion in registration and steadiness per- 
formance, reduced the tendency of the 
film to tear, and caused no apparent 
interference with piloting pins or sprocket 



teeth. Film with the Modified Negative 
form of hole can be used without limita- 
tion on equipment designed to run the 
present ASA Standard Negative and 
Positive perforation types and will posi- 
tion accurately on their registering 
mechanisms. Image steadiness of re- 
lease prints, exposed on the Bell & 
Howell type continuous printer, is im- 
proved by using the Modified Negative 
perforation throughout. 

We believe the consensus favors a 
single standard and that the complex 
situation due to the existence of multiple 
standards should not be permitted to 
continue indefinitely. On the basis of 
theoretical considerations and tests con- 
ducted on the Modified Negative per- 
foration, the adoption of such a perfora- 
tion seems to be a practical solution and 
a step toward the establishment of a 
single standard. 

Acknowledgment 

The problem of judging relative per- 
formance of films with different-shape 
perforation holes is a delicate one. 
Through the efforts of several people, 
much information, which is invaluable in 
determining a satisfactory solution, has 
been made available. The SMPTE 
Film Dimensions Committee under the 
chairmanship of Dr. E. K. Carver has 
played an important part in encouraging 
such investigations as might lead to a 
final settlement and perhaps to the 
establishment of a single universal per- 
foration standard. The author wishes to 
acknowledge the work of Carl L. 
Schaefer on the steadiness problem and 
his ? cosponsoring of the Modified Nega- 
tive perforation as a possible universal 
standard. The photoelectronic recorder 
was developed by Raymond W. Laven- 
der. 

References 

1. Proposed American Standard, Jour. 
SMPE, vol. 52, pp. 447-452, Apr. 1949. 

2. Report of the Subcommittee on Per- 
foration Standards. Jour. SMPE, vol. 
29, pp. 376-387, Oct. 1937. 



122 



August 1951 Journal of the SMPTE Vol. 57 



Discussion 

L. L. Ryder: How do you distinguish 
between lack of registration from per- 
foration deficiencies and the other factors 
that contribute to lack of registration? 

Mr. Lavender: The method described, 
will distinguish only steadiness components 
relative to the screen or relative to the 
perforations. Whether unsteadiness is due 
to perforation defects or design, or whether 
it is due to something within the projector, 
the camera or the printer, is something 
which has to be determined by other 
means. 

Mr. Ryder: The data was used to de- 
termine the more essential system of per- 
forating. Could that not also be partly 
attributed to the care of perforating, or 



the accuracy of perforating, rather than 
the type of perforation? 

Mr. Hill: There is no question that the 
accuracy of perforating definitely has a 
bearing on results. We were primarily 
comparing one film with another, and 
therefore in perforating these films we took 
care to see that the tools and machines 
were as nearly alike as possible. The 
punches and pilots were made to the same 
tolerances and, therefore, we feel that it 
is a fair comparison of types of perforation. 
I might add that you could locate photo- 
cells at various positions, perhaps on two 
successive perforations, or at the first and 
third on a frame, and, by the method Mr. 
Lavender has explained, get variations in 
perforation pitch and alignment. 



W. G. Hill: Modified Negative Perforation 



123 



Photoelectronic Method for Evaluating 
Steadiness of Motion Picture Film Images 



By R. W. LAVENDER 



Comparative data on the steadiness of motion picture film images are generally 
obtained by recording the qualitative observations of viewers. Recent prob- 
lems encountered in evaluating the relative merits of several types of per- 
forations, each of which was being considered as a universal 35-mm standard, 
necessitated the development of a method for obtaining specific quantitative 
steadiness data. An instrument which utilizes variable-area photoelectric 
recording techniques was devised to measure, indicate and record steadiness 
data of the motion picture image relative to the screen and/or perforation. 
Use of this instrument and a special test screen permits viewing of a projected 
motion picture test film while simultaneously measuring the image steadiness 
and recording the data measured. 



JL HE STEADINESS of a motion picture 
depends on the accuracy with which 
successive projected picture frames 
occupy the same position on the viewing 
screen. The positional variations of the 
frame image relative to the screen can be 
completely defined in terms of any one or 
combination of the following: 

(a) longitudinal position variation, 
Fig. la; 

(b) transverse position variation, Fig. 
Ib; and 

(c) rotational position variation, Fig. 
Ic. 

Although steadiness, as defined above, 
is a quantitative measurement of the 
positional variation of the motion picture 
frame image relative to the viewing 
screen, it is the subjective or apparent 



Presented on May 2, 1951, at the Society's 
Convention at New York, by R. W. 
Lavender, Ansco Division, General Aniline 
& Film Corp., Binghamton, N.Y. 



steadiness which is generally of primary 
importance. Thus, the present visual 
test method of evaluating steadiness by 
jury opinion is fundamental. Neverthe- 
less, specific quantitative data are fre- 
quently desired for the purpose of more 
accurately determining the magnitude, 
frequency, and source or sources of un- 
steadiness. For example, recently it 
was considered desirable to obtain 
quantitative steadiness data of film 
which had been perforated with several 
different types of perforations, namely, 
the Dubray-Howell, the Standard Nega- 
tive and the Modified Negative the 
latter proposed by W. G. Hill and C. L. 
Schaefer of Ansco. Each of the fore- 
going perforations was being considered 
as a universal 35-mm standard. 

In an effort to obtain basic compara- 
tive data on the relative steadiness of the 
above perforations, the photoelectronic 
recorder described herein was developed. 



124 



August 1951 Journal of the SMPTE Vol. 57 



IMAGE OF FRAME 
PROJECTED ON SCREEN 



LONGITUDINAL 



Fig. 1. Steadiness components 
of motion picture frame image. 

The results of tests conducted with this 
instrument relative to perforation steadi- 
ness plus others are described in W. G. 
Hill's paper, "Modified Negative Per- 
forations Proposed as a Single Standard 
for 35-Mm Motion Picture Film" (the 
paper immediately preceding in this 
JOURNAL). 

The subject recorder, in addition to 
being of some value as an adjunct to the 
visual test method of steadiness evalua- 
tion, has a further usefulness in that it 
can provide recorded data which will 
indicate the amount of unsteadiness con- 
tributed by the camera and printer and/ 
or projector. Further, these data are 
obtained concurrently with the visual 
inspection. If desired, the observer of 
the projected image on the screen may 
operate switches which will cause identi- 



fying marking "pips" to be made on the 
recorded chart for reference purposes. 

The instrument is basically a variable- 
area photoelectronic recorder in which 
movement of the projected frame or 
image, relative to the viewing screen, 
results in a change in the total light flux 
falling on one or more photocells. This 
is illustrated in Fig. 2, which shows the 
photocells mounted on the test screen on 
which is projected an image of the film 
including the perforations the gate of 
the projector having been opened to 
permit the projection of the full film 
width. Note that a longitudinal dis- 
placement of the picture frame, frame 
image and perforation image, results in a 
vertical.movement of the position of the 
boundary line between the cross-hatched 
and clear areas relative to the photocells. 

If the following assumptions are made: 

(a) the cross-hatched area, Fig. 2, is 
opaque and the clear area transparent; 

(b) the light intensity is constant and 
is uniformly distributed over the photo- 
cell window area; and 

(c) the sensitivity of the cathode 
surface of the photocell is approximately 
constant over the area chosen; 




Fig. 2. Positions of photocells on test screen. 
R. W. Lavender: Evaluating Film Steadiness 



125 




OUTPUT 




,+75 V 
REG. 



Fig. 3. Photocell demodulator channel elementary. 



then the position variations of the bound- 
ary between the cross-hatched and clear 
areas relative to the photocell windows 
will result in proportional changes in 
photocell output current. 

It is desirable and necessary that the 
constant of proportionality, for bound- 
ary position variations to output current 
or voltage change, should have the same 
value for each photocell. When this is 
the case, the output may be calibrated in 
terms of position, and the output data 
obtained from any one photocell may be 
directly compared with that from any 
other. In other words, a specific posi- 
tion displacement of the boundary be- 
tween the clear and opaque areas, 
parallel to any photocell, e.g., 1 in., will 
result in a current or voltage output 
change of one volt from any photocell. 
The above is practically accomplished by 
making the window in each photocell 
enclosure, Fig. 5, the same physical size 
and shape, and providing means in an 
external circuit whereby the maximum 
photocell output voltage may be ad- 
justed when the photocell window is 
fully within the clear area. More 
specific details on the actual circuit 
adjustments necessary to satisfy the 
assumed conditions are given under the 



heading Instrument Adjustment and Opera- 
tion, below. 

In the practical application of the pro- 
posed photoelectronic method for steadi- 
ness evaluation, it is, of course, necessary 
to filter out the steady-state frequency 
generated by the shutter in the projector 
and to replace the carbon arc with a 
voltage-stabilized incandescent lamp to 
obtain the required constant light in- 
tensity. 

Electronic Circuit Operation 

Those familiar with electronic circuit 
design fully appreciate the many differ- 
ent types of circuits which could be used 
to obtain a recorded output voltage di- 
rectly proportional to image displace- 
ment under the conditions noted above. 
Although considerable improvement can 
be made in the circuit, shown in Fig. 3, 
the results obtained with it were quite 
satisfactory. 

The operation of the circuit is briefly 
as follows: 

A fraction of the photocell output 
voltage, developed across the gain 
potentiometer in the control grid circuit 
of the pentode, Vi, is amplified by Vi 
and to a small extent by the transformer 
in its anode circuit. The secondary of 



126 



August 1951 Journal of the SMPTE Vol. 57 



BRUSH RECORDERS 















f 






























I 




















(4) DEMODULATOR 
FILTER -^ 


-* 
























































ICGULAT 
VOLTAGI 






1 


1 




I | 




-L 


1 




4 


1 






SUPPLY 






























J 



Fig. 4. Photoelectric steadiness evaluator for 
motion picture film images block diagram. 



this transformer is connected to a full- 
wave germanium diode bridge rectifier 
from which is obtained a d-c voltage 
proportional to the intensity of the 
pulsating light falling on the photocell. 
The twin "T" null-type filters, connected 
in cascade, effectively remove the steady- 
state ripple frequency components from 
the rectified d-c voltage. The output 
from the above filter circuit is connected 
to the grid of V 2 . This tube, connected 
as a cathode follower, is used principally 
as an impedance transformer. 

The low source impedance, character- 
istic of cathode followers, permits the use 
of a voltmeter as an output indicator and 
provides a convenient means for the 
mixing of outputs from different photo- 
cell channels. Thus, the recorders which 
are shown in the block diagram, Fig. 4, 




Fig. 5. Photocell housing; 
window 1/2 in. wide. 



may be connected directly, as indicated, 
to the output from the demodulator filter 
channels or, if desired, the outputs from 
the channels may be combined to obtain 
relative steadiness data. For example, 
the change in the output voltage from the 
channel supplied by photocell A, Fig. 2, 
due to longitudinal position variations of 
the image boundary, may be combined 
with the output voltage from the channel 
supplied by photocell E and the differ- 
ence or unbalanced voltage recorded. 
The voltage variations so obtained would 
be a measure of the motion of the film 
image relative to the perforation and 
would be indicative of the unsteadiness 
contributed by the camera and/or 
printer. 

To facilitate the mixing of the photo- 
cell demodulator channel outputs, two of 
them supply a positive output potential 
with increasing light, whereas that of the 
remaining two supplies a negative poten- 
tial. Aside from this output polarity 
reversal, the channels are electrically 
identical. 

A frequency-characteristic curve of the 
channel gain as a function of modulation 
frequency is shown in Fig. 6. Ideally, 
this response should be flat from approx- 
imately to 10 cycles/sec. 

A photograph of the steadiness evalu- 



R. W. Lavender: Evaluating Film Steadiness 



127 



F+-0 



I 2 3 4 5 6 78 910 
FREQUENCY- CYCLES/ SEC. 

Fig. 6. Frequency-output characteristics of demodulator channel. 



ator console and one of the console with 
the Brush Recorders mounted on a shelf 
in the back of the projection test screen 
are shown in Figs. 7 and 8, respectively. 

Instrument Adjustment and Operation 

The accuracy of the photoelectronic 
method for evaluating steadiness is con- 
tingent upon the conditions listed below: 

1 . The intensity of the projector light 
source during the test should be constant. 

2. The light flux distribution on the 
viewing screen, in the absence of film, 
should be uniform over the photocell 
window positions. 

3. The projector shutter speed should 
be constant; and if the null- type filters 



are used, these filters should be adjusted 
for the specific frequency generated by 
the shutter and the twice frequency rip- 
ple component resulting from the full- 
wave rectification of the amplified photo- 
electric a-c voltage. 

4. The windows or openings in the 
photocell enclosures, Fig. 5, should be 
square or rectangular and each should 
have the same physical size and orienta- 
tion relative to the photocell. 

5. The light sensitivity of the cathode 
surface of the photocell over the window 
area should be constant. 

6. The output voltage from each of 
the photocell channels should be ad- 
iusted to give the same value when the 




128 



Fig. 7. Steadiness evaluator console. 
August 1951 Journal of the SMPTE Vol. 57 



photocells are fully illuminated at their 
respective positions on the viewing 
screen. 

7. The differences in the sharpness 
between the clear and opaque areas of 
the film should be relatively small. 

8. The recorded voltage output, as a 
function of frequency, should be con- 
stant from approximately ^ to 10 cycles/ 
sec. 

9. The film density variations in the 
clear and opaque areas should be small. 

The practical operation and applica- 
tion of this instrument for evaluating 
steadiness will be readily understood if 
we consider, in somewhat more detail, 
the adjustment of the instrument for 
recording the longitudinal component of 
steadiness. Consider again Fig. 2. In 
this illustration, the photocell housings 
have been removed for convenient 
representation. In actual use, the aver- 
age position of the boundary between 
the cross-hatched and clear areas approx- 
imately bisects the windows of the en- 
closures. As previously stated, it is 
essential that the change in the output 



voltage from each of the photocell 
channels should be the same when the 
windows of the photocells are, first, fully 
within the clear portion of the image, 
and, then fully within the cross-hatched 
portion. This is conveniently done by 
setting the gain potentiometers in the 
grid circuits of Vi, Fig. 3, to zero and 
adjusting the meter-"zero set" potenti- 
ometers until the output meter in each 
channel indicates zero volts. The pic- 
ture image, Fig. 2, is then framed down- 
ward, fully illuminating the windows of 
photocells A, C, D, G and E. Having 
done this, the gain potentiometers in the 
grid circuits of Vi are adjusted until the 
output meters read midscale or one volt. 
The film image is then framed upward 
so that the cross-hatched portion of the 
image fully covers the windows of the 
photocells and the output meter readings 
are noted. If the meter readings are 
other than zero, it indicates that some 
light is being transmitted through the 
cross-hatched portion of the film, which 
may require compensation. The com- 
pensation is accomplished by readjusting 
the meter-set potentiometers to obtain a 




Fig. 8. Steadiness evaluator console and recorders back of test screen. 

R. W. Lavender: Evaluating Film Steadiness 129 




Fig. 9. Transverse position variations of frame image for 
two consecutive passes of test film through projector. 



zero reading on the meters and framing 
the image of the film downward, until 
the photocell windows are again fully 
within the clear area. The gain poten- 
tiometers are then increased until the 
output meters read midscale or one volt. 
If, when the film image is again framed 
upward, the output meter readings are 
greater than approximately 0.1 v on any 
channel, the process is repeated. This is 
seldom necessary, however, for with 
reasonable care in preparing the film, 
the cross-hatched density is very high 
compared with that of the clear area 
and compensation is not required. The 
channels fed by photocells B, H and F 
are adjusted similarly by moving the test 
projection screen transverse to the image. 

After the channel adjustments noted 
above have been made, the recorders are 
calibrated. In the tests conducted with 
the instrument, relative to the evaluation 
of the steadiness of the several perfora- 
tion proposals previously referred to, the 
calibration was set for one small chart 
division for each 0.01 -in. displacement of 
the image relative to the screen. This 
0.01 in. was equal to an equivalent dis- 
placement of 0.0002 in. at the aperture 
on the projector. 

The overall accuracy of the system is 
indicated in part by the similarity in the 
recorded chart patterns shown in Fig. 9. 
These curves represent the transverse 
positional variations between the image 
(photocell B), Fig. 2, and the perforation 
(photocell F) for two consecutive passes 
of the test film through the projector. 



A few of the photocell combinations 
which may be used for obtaining specific 
steadiness components are listed below. 

Steadiness Components of Frame Image Rela- 
tive to Screen 

1. Longitudinal Component output 
from channel fed by photocell A; 

2. Transverse Component output 
from channel fed by photocell B; and 

3. Rotational Component unbal- 
anced output from channels fed by 
photocell C and photocell D. 

Steadiness Components of Frame Image Rela- 
tive to Perforations 

1. Longitudinal Component unbal- 
anced output between channel fed by 
photocell A and channels fed by photo- 
cell E and photocell G connected in 
parallel through suitable decoupling re- 
sistors; and 

2. Transverse Component unbal- 
anced output between channel fed by 
photocell B and channels fed by photo- 
cell H and photocell F connected in 
parallel through suitable decoupling 
resistors. 

The photoelectronic method of evaluat- 
ing steadiness described herein has proven 
to be of value in supplying recorded quali- 
tative and quantitative steadiness data. 
These recorded data are particularly useful 
in supplementing the information ob- 
tained by the visual inspection method of 
steadiness evaluation. 



130 



August 1951 Journal of the SMPTE Vol. 57 



Sound Track on Eastman Color 
Print Film 

By C. H. EVANS and J. F. FINKLE 



The photographic image in the sound-track area of Eastman Color Print Film, 
Type 5381, is composed of metallic silver plus dye. The normal sensitometric 
specifications for sound negatives used in release printing on black-and-white 
materials are also suitable for negatives to be printed on Type 5381. The 
sound track should be printed by light which has been filtered in such a man- 
ner that the dye component of the developed image will be neutral. In gen- 
eral, the sound quality of neutral prints on Type 5381 is comparable with that 
of prints on Eastman Fine Grain Release Positive Film, Type 5302, but the 
latter has superior response at the higher frequencies. 



1_JASTMAN COLOR PRINT FILM, Type 

5381, is a 35-mm integral tripack three- 
color subtractive film, designed to be 
printed from picture negatives taken on 
Eastman Color Negative Film, Type 
5247. In processing a release print on 
Type 5381, the initial stages are common 
to the picture and to the sound track. 
First, the images are developed to 
metallic silver plus dye. Next, the film 
passes through a fixing bath which re- 
moves all undeveloped silver halide, and 
then through a bleach which converts all 
silver to silver bromide. Following the 
bleach, the sound-track area alone is 
treated by application of a reducing 
agent. This converts the silver bromide 
of the sound track back into metallic 
silver. The reducer is washed from the 
film by a water jet, just before the film 
enters a wash tank. From that point on, 



Communication No. 1402 from the Kodak 
Research Laboratories, a paper presented 
on May 4, 1951, at the Society's Conven- 
tion in New York, by C. H. Evans and 
J. F. Finkle, Eastman Kodak Co., Kodak 
Park Works, Rochester 4, N.Y. 



picture and sound track again receive 
identical treatment. The resultant 
sound-track image is composed of both 
dye and metallic silver. 

Sound-Track Printing and Densitometry 

In general, sound tracks on Type 5381 
are printed from black-and-white nega- 
tives. There are two variables in the 
printing operation which can be used for 
controlling sound quality. One of these, 
the amount of exposure, controls the 
print density. The other, the color 
quality of the printing light, controls the 
shape of the H&D (D log E) curve 
pertaining to the sound track. The 
characteristic curve of each individual 
layer is determined by the properties of 
its emulsion, and by the development 
which it receives. The latter is dictated 
by the requirements of the picture. Re- 
development of the sound-track silver 
after bleaching is a process which goes 
rapidly to completion, and so is not suit- 
able for regulating gamma. The char- 
acteristic curve of the film as a whole is 
the sum of the curves of the individual 



August 1951 Journal of the SMPTE Vol. 57 



131 



layers. Varying the relative exposures 
of these layers, by changing the color 
quality of the printing light, causes a 
change in the composite curve. Maxi- 
mum gradient is obtained when the light 
produces an image, the dye component 
of which is neutral, because then each of 
the individual layers contributes density 
throughout the range of total density. 
As it turns out, this condition yields the 
best sound prints, both variable-width 
and variable-density. 

Because the sensitivities of the individ- 
ual layers vary considerably among 
themselves, it is necessary to filter the 
printing light in order to obtain a neutral 
print from a black-and-white negative. 
A pack composed of several niters will be 
required. The combination of a photo- 
metric filter with color-compensating 
niters is recommended because it re- 
quires the least number of elements. 
This is important because it minimizes 
surface losses. Experimentally, it was 
found that the available exposure was 
doubled in changing from a 6-element 
to a 3-element filter pack. In printing 
sound, it is not necessary to include in the 
filter pack an ultraviolet-absorbing filter 
such as that used in printing the picture. 

To make neutral prints of proper den- 
sity on a Bell & Howell Printer, Model 
D, operated at 90 ft/min, it has been 
found necessary to use a high-intensity 
light system, utilizing a concave mirror 
and a 300-w tungsten lamp. 

In selecting filters to produce a neu- 
tral image, it is helpful to employ sensi- 
tometric methods. One manner in 
which this can be done is as follows: 
First, by use of a lib sensitometer a step 
tablet is made on a motion picture film, 
preferably on the type to be used for the 
sound negative. This is printed onto 
Type 5381 in the sound printer, using a 
combination of filters which is known to 
produce an approximately neutral image, 
for example, a Kodak Wratten No. 86 
Filter plus Kodak Color Compensating 
Filters, CC-20Y and CC-10M. The 
print is processed without redeveloping 



silver in the sound track. Then, by trial 
and error, any necessary changes are 
made in the filter pack until a visually 
neutral print is obtained. Next, the 
blue, green and red densities of the steps 
of this print are determined on a suitable 
densitometer, and are plotted in the form 
of H&D (D - log ) curves. This set of 
curves then serves as a standard with 
which other sets can be compared. 
Deviations from the standard will indi- 
cate quantitatively any changes in filters 
which may be required. To maintain 
maximum available exposure, a mini- 
mum of filters should be used. In 
changing a filter pack to obtain a neutral 
image, one should always be alert to the 
possibility of accomplishing this end by 
removing a filter rather than by adding 
one, for example, by removing magenta 
rather than by adding green. 

A typical set of standard curves ob- 
tained by use of a Western Electric 
RA-1100-B Densitometer is shown in the 
right-hand panel of Fig. 1. Integral 
blue, green and red densities of a neutral 
strip were determined by employing, re- 
spectively, the "blue-printing" filter sup- 
plied with the densitometer, a Kodak 
Wratten No. 58 Filter, and a Kodak 
Wratten No. 25 Filter. As a matter of 
general interest, a set of equivalent neu- 
tral density curves, determined from the 
same neutral strip, is shown in the left- 
hand panel of the figure. 

In densitometry of the composite silver 
and dye image, the visual method leaves 
something to be desired. The dyes ab- 
sorb visible light and, therefore, contrib- 
ute strongly to visual density, but they 
are quite transparent to infrared radia- 
tion. Since conventional sound repro- 
ducers utilize infrared-sensitive photo- 
tubes, the signal generated in such a re- 
producer by the sound track on Type 
5381 is attributable almost solely to the 
silver component of the image. Visual 
densitometry can, therefore, be quite mis- 
leading. For example, an effective den- 
sity of 1.6 in a variable-width print will 
have a visual diffuse density of approxi- 



132 



August 1951 Journal of the SMPTE Vol. 57 



2.0 



1.0 



DO I -I" 





0.0 



0.8 



1.6 0.0 



0.8 



1.6 



Log exposure ( relative) 

Fig. 1. Density versus log exposure for a neutral print (dye only) on Type 5381. 

Left: Equivalent neutral densities, magenta, M; cyan, C; and yellow, Y. 

Right: Integral densities, green, G; red, R; and blue, B. 



mately 2.6. Consequently, it is recom- 
mended that a physical densitometer be 
used for reading sound-track densities. 
It should be equipped with a phototube 
of the infrared -sensitive type used in re- 
producers. No filter should be used in 
the optical system. 

All sound-track densities referred to in 
the remainder of this paper were read on 
a Western Electric RA-1100-B Densi- 
tometer in which the usual blue-sensitive 
Type 929 phototube had been replaced 
by a Type 925 phototube. The heat- 
absorbing glass which is normally present 
in the optical system was removed. It 
has been found that densities of neutral 
sound track on Type 5381 read on this 
modified densitometer are in good agree- 
ment with the actual densities effective in 
a sound reproducer. 

Sound Tests 

Distortion, frequency-response, volume- 
level and signal-to-noise ratio tests have 
been made on Eastman Color Print 
Film. In variable-density prints, distor- 



tion was determined by the intermodu- 
lation method, 1 using 60 cps (cycles per 
second) and 1000 cps, while in variable- 
width prints it was determined by the 
cross-modulation method, 2 using a 9500- 
cps carrier frequency, amplitude-modu- 
lated at 400 cps. All of the negatives 
used were sensitometrically equivalent 
to the normal negatives employed in 
black-and-white release printing, or else 
they covered a sensitometric range in- 
cluding the normal. Variable-density 
negatives were exposed on Eastman Fine 
Grain Sound Recording Film, Type 
5373, while the variable-width negatives 
were exposed on Type 5372. 

Neutral prints were made from each 
negative. Prints exposed with unfiltered 
tungsten light were made from several of 
the negatives, and in some cases prints 
were made using tungsten light filtered 
by a Kodak Wratten No. 2B Filter, which 
absorbs ultraviolet. It will be conveni- 
ent at times to refer to either of the latter 
two types of print as a "white-light 
print." The context will make it clear 



Evans and Finkle: Sound on Color Prints 



133 



whether or not the ultraviolet-absorbing 
filter was used. This filter will be re- 
ferred to simply as the "No. 2B Filter." 
Experiments were also made in which the 
sound-track image was limited to two of 
the sensitive layers of the print material, 
but since the results were unfavorable to 
the use of this method they will not be 
presented. Finally, comparison prints 
from the same negatives were made on 
Eastman Fine Grain Release Positive 
Film, Type 5302, using unfiltered tung- 
sten light. In making all of these prints, 
a Bell & Howell Printer, Model D, was 
used. It was equipped with a Bell & 
Howell high-intensity tungsten light sys- 
tem, and was operated at the rate of 90 
ft of film per minute. Changes in the 
amount of exposure were accomplished 
by changing the diaphragm in the optical 
system, so the color quality of the expos- 
ing light remained constant. The volt- 
age supplied to the printer lamp was held 



at 105 v. It is interesting that no appre- 
ciable increase in available exposure 
could be obtained by raising the voltage 
above 105 v, because the increasing color 
temperature required the use of more 
filters to maintain a neutral image. 

The reproducer used in analyzing the 
prints was a standard Western Electric 
RA-1251-B Re-Recorder, with infrared- 
sensitive phototube. 

Variable-density intermodulation 
curves are shown in Fig. 2. Those 
drawn with a solid line pertain to neutral 
prints on Type 5381. In order to cover 
the desired range of sensitometric con- 
ditions, nine negatives were used, as indi- 
cated in the figure. The curves drawn 
with dashed lines in the central panel 
were obtained from comparison prints on 
Type 5302. They are quite similar to 
the curves for Type 5381 . Volume levels 
were also measured on the prints of Fig. 2. 
The prints on Type 5381 were found to 



20 



15 



10 



Hby 0.46 




>0.65 
N '0.55 



0.4 5_ _ 



IT by -0.56 



0.44 




Prints on 5302 
I I I 



D -0.66 
0.55 



0.45 




0.4 



0.6 0.8 0.4 0.6 0.8 0.4 



0.6 0.8 



Print density ( infrared) 

Fig. 2. Intermodulation. Neutral prints on Type 5381 from negatives on 
Type 5373, reference prints on Type 5302. 



134 



August 1951 Journal of the SMPTE Vol. 57 



run from 3 to 4 db higher in volume than 
corresponding prints on Type 5302. 

In Fig. 3 are shown additional inter- 
modulation curves. These compare a 
neutral print with two other prints, one 
exposed with unfiltered tungsten light, 
and the other exposed with tungsten 
light from which the ultraviolet was re- 
moved. A single negative, of normal 
density and gamma, was used. It will be 
noted that the optimum print density for 
the white-light prints is considerably 
higher than that of a neutral print. At 
the points of minimum intermodulation, 
the volume level of the neutral print is 7 
db above that of either white-light print. 
A portion of this difference is attributable 
to the lower optimum print density of 
the neutral print, the remainder to its 
higher gradient. 

Variable-density frequency-response 
curves are shown in Fig. 4. These have 
been corrected to show film losses only; 
scanning-slit losses are not included. 



20 



15 



10 



Neutr 






0.2 



0.4 0.6 0.8 1.0 

Print density (infrared) 



Fig. 3. Intermodulation. Comparison 
of white-light and neutral prints on Type 
5381, from normal negative on Type 

5373. 




-20 - 



100 



500 1000 
Frequency (cps) 



5000 10000 



Fig. 4. Variable-density frequency response, referred to zero level at 1000 cps. 

Comparison of white-light and neutral prints on Type 5381, from 

normal negative on Type 5373, reference print on Type 5302. 



Evans and Finkle: Sound on Color Prints 



135 



Each curve has been referred to zero 
level at 1000 cps. The curves drawn 
with solid lines pertain to prints on Type 
5381, while the curve drawn with dashes 
is a reference curve obtained by printing 
the same negative on Type 5 302 . Of the 
two solid curves, the upper one corre- 
sponds to a neutral print, the lower one 
to a print made with tungsten light 
filtered through a No. 2B Filter. The 
neutral print has somewhat better re- 
sponse at high frequency than does the 
white-light print, but both are inferior to 
Type 5302. 

For the determination of signal-to- 
noise ratio in variable-density prints, a 
negative was made which contained a 
1 000-cps recording, and a long section of 
unbiased, unmodulated track at the same 
density. Prints made from this negative 
were run on the re-recorder, and the rela- 
tive outputs of the two sections were 
found. An 8000-cps low-pass filter was 
used to eliminate high-frequency noise. 
The signal-to-noise ratio of a neutral 
print on Type 5381 was found to equal 



that of a print on Type 5302, but that of a 
white-light print was 5 db lower. 

To turn now to variable-width prints, 
cross-modulation curves obtained by 
using a negative recorded at several 
different densities are shown in Fig. 5. 
The family of curves at the left refers to 
neutral prints on Type 5381, while that 
at the right refers to prints on Type 5302. 
In each case, curves are shown for three 
different print densities. Negative-den- 
sity latitude does not vary greatly with 
print density and, at a cross-modulation 
product of 32.5 db, it averages 0,26 for 
prints on Type 5381, and 0.30 for prints 
on Type 5302. The optimal negative 
densities for the prints on Type 5381 are 
about the same as those for the prints on 
Type 5302. It is to be noted that the cor- 
responding print densities are about 0.3 
higher on Type 5381 than on Type 5302. 

Another set of cross-modulation curves 
is shown in Fig. 6. In this case, the 
negative was exposed at a single density. 
Each print made from this negative was 
exposed to a series of print densities. At 



.1 - 




10 
20 
30 
40 
50 



5381 




Dp 1.34 1.65 1.90 
I I I I . I 1 I I I 



5302 




I I 



Dp. 1. 10 1.31 1.56 
I I I I 1 I 



1.6 



2.0 2.4 



2.4 2.8 3.2 



2.8 3.2 1.6 2.0 
Negative density 

Fig. 5. Cross modulation, three different print densities, negative density 

variable. Neutral prints on Type 5381 from negatives on 

Type 5372, reference prints on Type 5302. 



136 



August 1951 Journal of the SMPTE Vol. 57 



the left is shown a pair of curves for 
white-light prints. The left-hand curve 
of this pair, drawn with dashes, corre- 
sponds to a print made with no filter, 
while the other curve refers to a print 
made with an ultraviolet-absorbing filter 
in the light beam. A reference curve, 
from Type 5302, lies near the center of 
the figure. The curve at the extreme 
right is for a neutral print on Type 5381. 
All four prints have a print-density lati- 
tude of approximately 0.23 at a cross- 
modulation product of 32.5 db. The 
optimal print density of the neutral print 
is considerably higher than that of a print 
on Type 5302. White-light prints, how- 
ever, have optimum print densities which 
are too low for good wearing quality. 

Figure 7 presents frequency-response 
curves measured on variable-width 
prints. The individual curves have been 
referred to zero level at 1000 cps. Three 
prints on Type 5381 are represented by 



10- 



o -20 

j, 

o -40 
u 

-50 



No Filter 28 FllUr 




9381 5302 5381 

W.L. Neutral 



0.4 0.8 1.2 1.6 2.0 2.4 
Print density (infrared) 

Fig. 6. Cross modulation, single nega- 
tive density, print density variable. 
Comparison of white-light and neutral 
prints on Type 5381, from normal nega- 
tive on Type 5372, reference print on 
Type 5302. 



0) 

I -,o 

o 



-15 



-20 



5381 
Neutral- 
W.L.- 
W.L. + 2B 



5302 




.L.+2B 



W.L.\ 



100 



500 1000 
Frequency (cps 



5000 10000 



Fig. 7. Variable-width frequency response, referred to zero level at 1000 cps. 

Comparison of white-light and neutral prints on Type 5381, from normal 

negative on Type 5372, reference print on Type 5302. 



Evans and Finkle: Sound on Color Prints 



137 



curves drawn with solid lines, while a 
reference curve, obtained from a print on 
Type 5302, is drawn with dashes. The 
high-frequency losses shown do not in- 
clude scanning-slit losses. Of the three 
curves for Type 5381, the bottom pair, 
which are scarcely distinguishable from 
each other, pertain to white-light prints 
made with and without the ultraviolet- 
absorbing filter. The upper solid curve 
was read from a neutral print. At high 
frequencies, this print has definitely bet- 
ter response than the white-light prints, 
but all three are inferior to Type 5302 in 
this respect. At 1000 cps, the volume 
level of the neutral print was 0.9 db 
lower, and that of each white-light print 
was 1.5 db lower, than that of the print 
on Type 5302. 

Signal-to-noise ratio in variable -width 
prints was determined by two different 
methods. The first method is similar to 
that used for variable density, the level of 
unmodulated, unbiased track being com- 
pared with that of a recorded 1000-cps 
signal. In a variable-width print, the 
noise which is measured in this manner 
arises chiefly from the clear areas of the 
print. Again, an 8000-cps low-pass 
filter was used to cut off high-frequency 
noise. Signal-to-noise ratio for the refer- 
ence print on Type 5302 was found to be 
3.1 db higher than the value obtained 
from a neutral print on Type 5381, and 
2.4 db higher than that obtained from a 
print made with unfiltered tungsten 
light. 

By the second method, noise measured 
on a section containing a 10,000-cps 
record made at 80% modulation, was 
compared with the signal level of a 1 000- 
cps record. In this case, an important 
contribution to measured noise is made 
by the granularity of the boundary be- 
tween the image and the clear area of the 
print. The 8000-cps low-pass filter in 
the measuring circuit serves to remove the 
10,000-cps signal, leaving only the com- 
ponents of noise with frequencies below 
8000 cps. Signal-to-noise ratio for the 
reference print on Type 5302 turned out 



to be 1.5 db higher than the value for a 
neutral print, and 1.1 db higher than the 
value for a print made on Type 5381 with 
unfiltered tungsten light. 

It will be noted that both types of vari- 
able-width noise measurement indicate a 
slight superiority of the white-light over 
the neutral print. The low print den- 
sity of the white-light print, however, 
would probably lead to a reversal in this 
relationship after repeated projection. 

As indicated previously, the entire 
series of tests just outlined was printed 
without varying the lamp voltage. The 
color quality of the exposing radiation 
was thus held constant throughout a 
given print. Limited variable-density 
intermodulation tests were made in 
which the exposure of "neutral" prints 
was varied by changing the lamp voltage. 
No change was made in the filter pack; 
therefore, the color balance of the image 
changed with density level. The dia- 
phragm opening, however, was carefully 
chosen to yield optimum print density at 
a color balance close to neutral, when 
printing from a negative of average den- 
sity. The resulting distortion curves did 
not vary greatly from those obtained by 
the other method. In controlling expo- 
sure by means of lamp voltage, care must 
be exercised to avoid large departures 
from neutrality, as these would be detri- 
mental to quality. Other experiments 
made in this connection, on both vari- 
able-density and variable-width prints, 
have indicated that departures from neu- 
trality which could be corrected by a 
change of 0.1 in the density of a color- 
compensating filter, can be tolerated. 

Conclusions 

Satisfactory sound prints can be made 
on Eastman Color Print Film from nega- 
tives which are exposed and developed 
according to standard practice. It is not 
necessary to use negatives of abnormal 
density or contrast. The dye-plus-silver 
sound track which is obtained is well 
suited to existing reproducers. 



138 



August 1951 Journal of the SMPTE Vol. 57 



Prints should be exposed with radiation 
of a quality which will produce an ap- 
proximately neutral image in the sound 
track. Printing with unfiltered tung- 
sten light is not recommended for either 
variable-density or variable-width sound 
tracks, because in each case the resulting 
prints are inferior to neutral prints in 
some respects. Although an ultraviolet- 
absorbing filter is necessary to preserve 
correct color balance in making prints 
from color-picture negatives, it has no 
appreciable effect on the balance to tung- 
sten light when printing from black-and- 
white sound negatives. 

Acknowledgment 

We are pleased to acknowledge the 
assistance given by several members of 
the Color Process Development Depart- 
ment, Kodak Research Laboratories, 
with whom we have conferred on prob- 
lems relating to exposure and develop- 
ment. 

References 

1. J. G. Frayne and R. R. Scoville, "Analy- 
sis and measurement of distortion in 
variable-density recording," Jour. 
SMPE, vol. 32, pp. 648-673, June 1939. 

2. J. O. Baker and D. H. Robinson, 
"Modulated high-frequency recording 
as a means of determining conditions 
for optimal processing," Jour. SMPE, 
vol. 30, pp. 3-17, Jan. 1938. 

Discussion 

John Stott: I believe Eastman Color 
Positive Film has speed relationships within 
the three layers which make it possible to 
print this film with essentially tungsten 
illumination with a 2B filter in the light 
source, so long as you use the Eastman 
Color Negative Film as your negative 
material. If that is the case, why is it 



not possible when you make the sound 
track, if you are looking for a neutral 
sound track, to use a piece of Eastman 
Color Negative Film that has been fixed 
out and use that as your filter? 

C. H. Evans: I think that would be 
possible. We haven't used that method. 
It might take some color compensating 
filters in addition. 

John P. Byrne: My question is one of an 
amateur regarding color. I don't know 
anything about it, practically, but we will 
have to think in terms of color at the Signal 
Corps from now on, I believe. How do 
you get your three separate curves, each 
one from a single emulsion layer? Are 
they exposed in a sensitometer to three 
different filters to get the cyan, magenta 
and yellow values? If this is the case, how 
do you superimpose those three to get your 
density equivalent? 

Mr. Evans: Do you refer to those curves 
which we showed in Figure 1? 

Mr. Byrne: Yes. 

Mr. Evans: Those were read on the 
entire film. That is, we had a single 
neutral densitometric dye strip, without 
any silver. The three integral density 
curves were read on the ERPI (Electrical 
Research Products, Inc.) Densitometer. 
The first curve was read using the blue 
printing filter; the procedure was then 
repeated on the same strip using the green 
filter, and again, using the red filter. The 
densities determined in this way are integral 
densities and they don't really separate 
completely the individual contributions of 
each of the three layers. 

J. G. Frayne: Are these losses that you 
report at high frequencies inherent in the 
dye structure? Or are they brought about 
by the silver sulfide in your process? 

Mr. Evans: This is not a sulfiding process. 
You just get silver and dye. I would say 
that such losses are inherent in a tri-pack 
film, where you have to print in all three 
layers. 



Evans and Finkle: Sound on Color Prints 



139 



Simultaneous High-Speed Arc Photography and 
Data Recording With a 16-Mm Fastax Camera 

By EUGENE L. PERRINE and NELSON W. RODELIUS 



In order to correlate photographs with other recorded data, the optical system 
of a galvanometer oscillograph was modified so that it could record on the film 
in the exposure aperture of a 16-mm Fastax camera. The addition of the 
galvanometer system required no permanent alterations of the Fastax camera 
and provided a record in the form of a spot which moved horizontally in the 
field of view when the film was projected. 



A S 



HAS BEEN the case in most other 
high-speed motion pictures of welding 
arcs, the photographs made by us were 
only one phase of a study of the arcs. 
Other information was recorded simul- 
taneously by pen recorders and a six- 
channel galvanometer oscillograph. 
After the experiments were partially 
completed it was found impossible to 
correlate the action in the motion pic- 
tures with the other recorded informa- 
tion. To overcome this difficulty, a 
galvanometer was added to the Fastax 
so that the same signal that was recorded 
on one channel of the oscillograph could 
also be recorded on the Fastax film. 
With this arrangement, it was possible to 
relate any action seen in the picture to 
variations in the recorded data. 

The photographs required for welding 
arc studies are close-ups. Usually only 



Presented on May 2, 1951, at the Society's 
Convention at New York, by Eugene L. 
Perrine and Nelson W. Rodelius, Armour 
Research Foundation of Illinois Institute of 
Technology, 35 West 33 Street, Chicago 16, 



the tip of the electrode, the arc, and a 
small area of the piece being welded are 
included in the field covered. In most 
cases a field one-half inch high was ade- 
quate. To cover this area without 
placing the lens too close to the arc, a 
113-mm focal length, //4. 5 Bausch & 
Lomb Tessar was used. The mounts for 
this and similar lenses used in our labora- 
tories were made in our own shop. 
They consist of a brass tube with adapters 
to fit the different lenses and a series of 
interchangeable tubes of various lengths 
which telescope with the lens tube and 
are fitted to the lens mount of the camera 
(Fig. 1). With these tubes and a series 
of lenses ranging in focal length from 17 
mm to 6 in., we are able to focus at any 
distance from infinity to less than one 
inch. They make possible any desired 
image size on the film up to a magnifica- 
tion of ten times. 

The brightness of various welding arcs 
differs over a range of more than one 
hundred to one, but in all cases it is very 
high. In addition to the use of small 
apertures, it was necessary to use filters 



140 



August 1951 Journal of the SMPTE Vol. 57 






Fig. 1. Lenses, adapters, and extension tubes used with the Fastax camera. 



to reduce the light reaching the film. 
Filter combinations having factors of 
about fifteen were used with Eastman 
Super X film, at 5000 frames/ sec, and 
apertures of from //1 6 to//64. These 
filter combinations were also used to 
select various portions of the spectrum 
when it was desirable to accentuate cer- 
tain parts of the arc. Pictures made 
with Kodachrome film and neutral- 
density filters were found less satisfac- 
tory than those made on black-and-white 
film, because of the shorter scale of the 
Kodachrome. A special holder was 
constructed for the filters (Fig. 2). This 
holder also held a cover glass which pro- 
tected the filters from splattering metal. 
A carriage mounted on a track carried 
the welding electrode. A camera sup- 
port was constructed and attached to the 
carriage so that the camera always fol- 
lowed the arc during the operation. A 
microswitch mounted on the track was 
operated by the carriage to start the 
camera. Manual operation of the 
camera was sometimes more desirable in 




Fig. 2. Filter holder. 

order to make possible the photograph- 
ing of the arc at the most advantageous 
moment, e.g., when the arc was least 
obscured by smoke. 

The timing-light in the Fastax was 
used to provide a record of camera 
speed, but after a few films had been 
viewed and the data recorded by the 



Perrine and Rodelius: High-Speed Arc Photography 



141 




Fig. 3. Galvanometer assembly on the Fastax camera. 



oscillograph examined, it was apparent 
that more than a record of camera speed 
was needed to relate the action to the 
recorded data. The use of synchroniz- 
ing pulses on the timing-light of the 
camera and one channel of the oscillo- 
graph was considered. This would have 
required the construction of a system for 
generating coded pulses and also the 
additional work of a frame-by-frame 
examination of the film to associate the 
marks on the edge of the film to the re- 
lated frame. Instead of using the syn- 
chronizing pulses, a way was devised for 
mounting one of the galvanometers 
from the oscillograph on the Fastax 
camera. 

In making this addition to the camera, 
two major problems had to be solved. 



First, the galvanometer system had to be 
attached to the camera in such a way 
that the future operation of the camera 
was unimpaired. It was desirable, al- 
though not mandatory, to make the 
additions in a fashion which would leave 
the camera available for other work dur- 
ing any break in the arc study. Second, 
the light from the galvanometer optics 
had to be improved to provide adequate 
exposure on the faster-moving film of the 
camera. 

The first of these problems was solved 
by folding the optical path of the gal- 
vanometer system and bringing the light 
beam into the camera through a hole cut 
in the top of the lens extension tube. 
Figure 3 shows the entire assembly, in- 
cluding galvanometer, light source, mir- 



142 



August 1951 Journal of the SMPTE Vol. 57 



Fig. 4. Optical system of 
galvanometer mounted 
on Fastax camera. 



CYLINOERICAL 
LENS 



MIRRORS 



CAMERA 
LENS 



LAMP 




GALVANOMETER 
LENS (SPHERICAL) 
AND MIRROR 



MOVING 
FILM 



rors and lenses. This assembly was 
mounted on a piece of f-in. plywood 
which provided a rigid support; it was 
easily held on the side of the camera with 
two clamps, and could be temporarily 
removed from the camera without loss of 
adjustments. First-surface mirrors were 
used throughout. The mirror mounted 
inside the extension tube was placed 
sufficiently below the optical axis of the 
camera so that none of the light passing 
from the camera lens to the film was 
intercepted. This was to avoid any 
change in the exposure of the picture. 
Because the apertures used were small, 
this was easily accomplished. Inter- 
ference would probably be inevitable 
with high relative apertures. Focus of 
the light spot and amplitude of the gal- 
vanometer were set with the lens re- 
moved from the camera so that the spot 
could be observed directly in the expo- 
sure aperture. The view-finder could 
not be used because the light entered 
the aperture from below the axis and 
was imaged at the top of the aperture. 
Rays following this path never enter the 
relay lens in the view-finder. 

When operated at 5000 frames/ sec, 
the film in the 16-mm Fastax camera 



moves about five times the paper speed 
used in the oscillograph from which the 
galvanometer record was obtained. The 
paper has a sensitivity nearly as great as 
Eastman Super XX film, so that no 
exposure increase is obtained with the 
recording material. The light source 
was a 6-8 v, 50-cp auto headlight bulb 
which was turned so that the optical sys- 
tem imaged the edge of the filament. 
To increase the brightness of the spot 
during exposure, the voltage on the bulb 
was advanced to just below the burn-out 
value. Also, two cylindrical lenses were 
added to the system. One placed near 
the lamp imaged it on the moving mirror 
of the galvanometer. A second cylinder, 
just above the lens extension tube, 
shortened the line image resulting from 
the first cylinder to a slightly elongated 
spot (Fig. 4). This spot was of adequate 
brightness to compensate for the in- 
creased writing speed in the camera. 

The galvanometer record appeared as 
a spot which moved horizontally in the 
bottom of the frame of the projected 
motion pictures. The spot size was 
slightly larger than the thickness of the 
coiled filament in the lamp used. Only 
slight improvement could have been 
obtained by using a slit over the lamp or 



Perrine and Rodelius: High-Speed Arc Photography 



143 



the first cylindrical lens, because of the 
low resolving power of the optical sys- 
tem. As a result, the traces obtained on 
the galvanometer oscillograph, which 
has a much greater swing than is pos- 
sible on 16-mm film, gave a more precise 
record than was obtained on the Fastax. 
However, the records obtained directly 
on the Fastax frame made it possible to 
see what electrical changes were associ- 
ated with the action that was photo- 
graphed, and when it was desired, an 
oscillogram was made simultaneously 
with the motion picture so that precise 
measurements could be made of the 
trace. 



Examples of other uses for the gal- 
vanometer-Fastax system are: (1) the 
firing of a flash bulb where the filament 
burn-out time is to be related to the 
burning; and (2) the operation of an 
electrically driven impact tool where the 
loading of the motor at different portions 
of the cycle is being studied. The sys- 
tem would be useful in many other 
applications where additional data are 
needed to determine the exact relation- 
ship between controlling or controlled 
signals and the action photographed, or 
where several slightly different opera- 
tions must be associated with their re- 
spective electrical counterparts. 



144 



August 1951 Journal of the SMPTE Vol. 57 



Forum on 

Motion Picture Theater Acoustics 



THIS FORUM was sponsored by the SMPE Atlantic Coast Section and the Acoustical 
Society of America, and was held on June 7, 1949, at New York, William H. Rivers 
presiding, and Professor Leo L. Beranek acting as Moderator. 



Chairman William H. Rivers: This is 
rather an unusual type of meeting for us 
to have, but it seems highly worth while. 
The main gain from this meeting is the 
technical discussion and the conclusions 
that may be taken away with us. [After 
announcements, Mr. Rivers turned the 
meeting over to the moderator. ] 

Moderator Leo L. Beranek: I think we 
will do best today if we treat this meeting 
as an informal one, and lay ourselves 
open to asking and answering questions, 
without worrying about whether this is 
going on the record or not. 

This Forum came to be organized as 
the result of a letter received a scant 
month past, and addressed to the SMPE 
Secretary, from Mr. Lucas, of the British 
Thomson-Houston Company, Ltd., say- 
ing that James Moir was going to be in 
New York about this date. We thought 
it would be helpful, knowing the papers 
that he has published in this field, to learn 
his thoughts on motion picture theater 
design, so we cabled him and he con- 
sented to be with us today. 

We thought it might also be interesting 
to learn about motion picture theater de- 
sign in the Scandinavian countries. 
Uno Ingard, of Chalmers University, 
Gothenburg, Sweden, studying at MIT 
in the Acoustics Laboratory, was asked 
if he would speak on the state of Scan- 
dinavian motion picture theater design. 



He hesitated at first because, he said, 
there are other people who are experts in 
this field, and he didn't want to speak as 
one of the experts. But he did consent 
to tell us the state of the art as he knows 
it. 

We felt that the important objectives 
of this meeting should be: (a) to ex- 
change information on an informal basis; 
(b) to establish what, if any, are the 
essential differences between practices in 
Europe and practices in the United 
States; and (c) to gain ideas on how to 
better the practices of our own countries. 

Having obtained the interest of our 
Forum visitors, we proceeded to assemble 
a panel of local experts, who will lead the 
discussion and answer questions from the 
audience. These men reserve the right 
to change their minds if they think better 
of their answers at some later date. [The 
panel personnel are listed on p. 159 of 
this Journal.] 

I do not wish to give a speech, but I 
would like to give the general basis of the 
subject of our discussion. 

When sound pictures were first being 
tried out around the country, they were 
shown in auditoriums, with rather bad 
acoustics, that is, the reverberation times 
were high. It soon became obvious that 
something would have to be done to the 
halls if sound motion pictures were to be 
acceptable. So, a trend developed in the 



August 1951 Journal of the SMPTE Vol. 57 



145 



direction of placing a lot of absorbing 
material in the rooms, with the result that 
most theaters became very "boomy." 
This happened because the absorbing 
materials selected were efficient only at 
the higher frequencies. Then, studies 
were made in the laboratories of some of 
our larger manufacturers of sound sys- 
tems. These studies led to the establish- 
ment of criteria for motion picture design. 
One particular set of studies led to the 
issuing of a bulletin by the Research 
Council of the Academy of Motion Pic- 
ture Arts and Sciences on May 30, 1 932, 
on "Theatre Acoustic Recommenda- 
tions." In it is a graph of optimum re- 
verberation times versus room volume. 
Also, Potwin and Maxfield published a 
paper in which they set forth another 
curve of optimum reverberation times, 
much the same as the SMPE curve for 
small rooms, but indicating somewhat 



higher reverberation times for large 
rooms. 

It has been my general observation 
that the recommendations set forth by 
the Academy of Motion Picture Arts and 
Sciences and by Potwin and Maxfield 
have not been adhered to in actual 
theater design in this country. I believe 
that most movie theaters are much 
deader than the optimum reverberation 
characteristics shown in these booklets 
would indicate. 

I sincerely hope that we shall discuss 
the trends in the design of motion picture 
theaters, both with regard to reverbera- 
tion time and room shaping. I would 
not be surprised if we should agree that 
the SMPE characteristics need revising. 
(At this point, Dr. Beranek introduced 
Mr. Moir who presented his paper, for 
which see the following pages of this 
Journal; then Mr. Ingard presented his 
paper which is also in this issue.) 



146 



August 1951 Journal of the SMPTE Vol. 57 



Pulse Methods 

in the Acoustic Analysis of Rooms 



By J. MOIR 



Experience in installing large numbers of a standard sound-film equipment 
in theaters indicated that sound quality was not related to the overall fre- 
quency characteristic or the reverberation time. A pulse technique is de- 
scribed which gives a direct picture of the direct and reverberant sound at 
any location. The value of the reverberation-time concept as presently 
defined is questioned and recommendations for the optimum design of theaters 
are given, based on the results of pulse analysis. 



T, 



HERE APPEARS TO BE little doubt 

that most first-order defects in the 
acoustical performance of a room are 
removed by the application of Sabine's 
analysis 1 and recommendations. Experi- 
ence appears to indicate, however, that 
the second-order defects, though still im- 
portant, are not corrected by more 
meticulous application or by elaboration 
of Sabine's analysis. This is not a state- 
ment that can be shown to have precise 
mathematical justification, but is some- 
thing that grows upon one as a result of 
daily contact with the problems. 

In our particular case, we were en- 
gaged before World War II in installing 
sound-film reproducers of standard de- 
sign in a large number of theaters, and 



Presented on June 7, 1949, as part of the 
Forum on Motion Picture Theater Acous- 
tics, sponsored by the SMPE Atlantic Coast 
Section and the Acoustical Society of 
America, held at New York, by James 
Moir, British Thomson-Houston Co., Ltd., 
Rugby, Warwickshire, England. 



we found that the results at the patron's 
ear varied all the way from very good to 
"not so good." The differences were 
sufficient to justify an investigation. As 
a first step, our Service Division was 
asked to provide us with a list of theaters 
in order of merit, all theaters listed 
having nominally identical equipment. 
When the list was studied in detail it was 
found that theaters listed as "above 
average" were all praised because of 
their "good intimacy," a factor which 
we think is termed "good presence" in 
the United States. The importance of 
this factor has been further confirmed 
during additional postwar investigations 
into the public preference in sound 
quality. In two areas checked, theaters 
having equipment of 1930-1932 design 
were preferred, though postwar equip- 
ment made by all the leading firms was 
available in the area. The result is sur- 
prising because the frequency response 
was very poor and wow and flutter were 
high, by current standards. In both 



August 1951 Journal of the SMPTE Vol. 57 



147 




CM 



Frequency, cycles per sec. 



Fig. 1. Reverberation time in different positions in auditorium, 
a and b: sound quality good; c and d: sound quality bad. 



theaters, the "intimacy" was particu- 
larly good. 

Reverting to the prewar investigation, 
after a preliminary check to make certain 
that no normal defects existed, we began 
to make a more extensive survey of those 
factors such as acoustic frequency re- 
sponse, reverberation tiirie, etc., factors 
which are known to be of importance 
though they are not normally checked in 
detail on every installation. 

Frequency response was not found to 
present any consistent explanation of the 
variation in results and this point will 
not be further discussed. 

For various reasons, the differences 
were considered to be acoustical and we 
therefore made a more detailed survey 
of the reverberation time/frequency 
volume relation. No consistent explana- 
tion was found. The results in one par- 
ticular theater, typical of many others, 
are indicated in Fig. 1, from which it 
will be seen that the differences which 
do occur are small and randomly dis- 
tributed. The test technique was con- 
ventional, a Neuman high-speed level 
recorder having been used, while the 
depth and frequency of the modulation 
of the test tone could be varied over 
wide limits. 



We did have some indication, how- 
ever, that a greater proportion of the 
good theaters were to be found with 
reverberation time below, rather than 
above, the optimum time/volume rela- 
tion. The results of twelve of the thea- 
ters in the first group tested are shown in 
Fig. 2. At the time, this was thought 
to be due to the preferred reverberation 
time/volume curve being nonoptimum, 
but we now feel that it is of more funda- 
mental significance. This point will be 
discussed presently. 

Experience gained during this part of 
the investigation confirmed that the 
sound-quality preference was based al- 
most entirely upon the closeness of asso- 
ciation of sound and picture, the quality 
we termed "intimacy," and we came to 
regard this as being connected in some 
way with the ratio of direct to reflected 
sound. 

Preliminary attempts to measure this 
were made, but without success until we 
devised the pulse techniques to be de- 
scribed. This enabled the direct and 
reflected components to be separated on 
a time basis and is probably best under- 
stood by referring to Fig. 3, a schematic 
layout of the equipment used. 



148 



August 1951 Journal of the SMPTE Vol. 57 



> o o 

o o o 

v> 

Theatre volume, 1000 cu.ft. units 



-Optimun 






Fig. 2. Theater volume/reverberation time /sound quality results. 
Black circles: sound quality above average. 



loud.peak.r 




. Tuning Condenser 
ncl Warble Condenser 



Msec Level 
Recorder 



Fig. 3. Setup for acoustic survey in auditorium. 



The output from a variable-frequency 
(audio) oscillator is applied to the input 
of the theater amplifier through a motor- 
operated cam switch, which can be set to 
close circuit for any period between 
and 50 msec, repeating this at intervals 
of 1 sec. The frequency of the test tone 
is set on the oscillator dial in the normal 
way. This tone pulse is radiated by the 
theater loudspeakers and is picked up by 
a sound-cell type of microphone, ampli- 
fied and applied to produce a vertical 
trace on a cathode-ray tube. Horizontal 
deflection of the cathode-ray-tube beam 



is initiated by the application of the 
pulse to the loudspeakers, the spot mov- 
ing uniformly from left to right in about 
0.5 sec. Thus, in free space, with no 
reflections present, the cathode-ray-tube 
picture consists of a vertical pulse spaced 
from the origin by a distance propor- 
tional to the distance between loud- 
speaker and microphone. With reflec- 
tions present, each reflected pulse is 
spaced from the initial pulse by an 
amount directly proportional to the 
difference in path length between the 
direct and reflected components. 



J. Moir: Acoustic Analysis 



149 




Fig. 4a-4d. Results obtained for theater equipment under 

open-air conditions; 

4e-4k. Results obtained for equipment in theaters 
ranging from above average to well below average. 




Goo<! 



150 



Fig. 5. Changes from bad to good sound quality. 
August 1951 Journal of the SMPTE Vol. 57 



250*** 



The first four pictures of Fig. 4 illus- 
trate the results obtained for the theater 
equipment under open-air conditions. 
The pulse at the input to the theater 
amplifier is shown in Fig. 4a, the result- 
ing pulse at the amplifier output, in 
Fig. 4b. Speaker performance is illus- 
trated by Figs. 4c and 4d, taken 4 ft 
from the high-fidelity horn on the axii>, 
4c and 30 off the axis, 4d. Pulse shape 
is seen to be substantially unaltered by 
the electroacoustic equipment. 

The remaining pictures, Figs. 4e 
through 4k, are selected to show typical 
results in theaters ranging from above 
average, Fig. 4e, to well below average, 
Fig. 4k. In the good location, Fig. 4c, 
the picture is seen to consist of a well- 
defined direct pulse followed by a con- 
tinuous structure of reflections 15 db 
below the direct sound, whereas the 
"below average" theater produces a 
picture, Fig. 4k, in which the direct 
pulse is almost obscured by a whole series 
of reflected pulses of greater amplitude, 
extending for at least 300 msec after the 
direct sound. It is worthy of note that 
in this theater, the frequency-response 
curve was the best of a group of twenty 
theaters tested about that time, whereas 
the sound quality was rated as the worst 
of the group. The reverberation time 
was close to, but a little above, the 
optimum value. 

Theaters in which good and bad listen- 
ing positions occurred were of particular 
importance in the investigation, insofar 
as all other factors remained constant. 
Figure 5 illustrates a particular example, 
where the Service Division was able to 
draw our attention to two seating posi- 
tions, fairly close together, but giving 
widely different subjective results. Pulse 
pictures taken at two frequencies in both 
locations are shown in Fig. 5 as typical 
of our findings, and it will be seen that 
strong reflections occur in this bad loca- 
tion about 100 msec after the direct 
sound. 

A large number of similar results could 
be quoted, but it is probably more to the 



point to mention that we have found no 
instance of a picture, similar to Fig. 4k, 
being obtained at a point at which the 
sound quality was considered to be good. 
This is true, irrespective of whether the 
reverberation time was above or below 
the optimum. 

It should be noted particularly that 
the test method checks the combination 
of hall and loudspeaker. In a theater it 
is this combination that is important, for 
it has been possible to minimize many 
hall defects by appropriate horn design. 

The relationship between reverbera- 
tion time and the pulse picture is of 
interest. If a uniform rate of decay of 
the total sound-energy density is secured, 
an attenuation of 15 db in 50 msec 
corresponds to a reverberation time of 
0.2 sec, a figure which is certainly on the 
short side. The figure of 50 msec can 
be considered only approximate at this 
stage in the investigation, but if it were 
doubled, the reverberation time would 
still be well below any suggested optimum 
for a theater of 1500 seats. The dis- 
crepancy is large and one is tempted to 
reflect upon our present conception of 
reverberation time, defined as "the time 
for a 60-db decrease in the mean sound 
energy density." It would appear un- 
necessary to consider the contribution of 
reflected components attenuated by 
more than 20 to 30 db. If the sound- 
energy decay in an enclosure were, in 
fact, a true exponential curve, neglect 
of the section of the decay curve below 
30 db would not alter the reverbera- 
tion time as now defined. However, ex- 
perimental evidence supported by theo- 
retical conclusions suggests that a true 
exponential decay is the exception rather 
than the rule. A typical decay curve, 
taken with a frequency-modulated tone 
is indicated in Fig. 6, where at least four 
different rates of decay might be deduced. 
If a modulated test tone were not used, 
the departure from a smooth exponential 
curve would be still greater, and we are 
inclined to believe that a test technique 
tends to be judged by its efficiency in 



J. Moir: Acoustic Anal/ sis 



151 



o o o o 


o c 


O 


O 


o o o 


( 




Revet 


Tin** 














/ 


J 










/ 


10 






.- 


*-M*- 


/ 


II 










/ 


20 








ML/"*^ 


/ 


JZSdb. 








/" 


__* 


30 






A^ 


/ 




35 






/ 






40 




> 




M 




45 




C 


o o 


O O 


o o o 


O O O 


o o o < 



Fig. 6. Multiple decay rates. 

turning a nonuniform decay into a 
smooth exponential decay. In doing 
this, we rather suspect that much that is 
of importance is obscured. 

We would suggest that a listening 
point is poor if there is discrete mid- 
frequency reflection delayed by more 
than 50 to 100 msec and attenuated by 
less than 20 db. If this is correct, we 
should not be worrying about decay 
periods of 60 db or time intervals in 
seconds, but should direct our attention 
to the details of the decay during the 
first 20 db (or perhaps 100 msec), as we 
believe that the acoustical character of a 
room is almost completely determined 
during this initial time interval. There 
appears to be strong evidence to support 
a review of our reverberation-time defi- 
nition, to place more weight on the 
initial 20 db of decay. 

Earlier in the paper it was noted that 
preferred theaters appear to fall below, 
rather than above, the current optimum 
curve. On the basis of the results re- 
ported, it is suggested that this is prob- 
ably not due directly to the fact that the 
best reverberation time is to be found on 
any alternative optimum curve, but is 
due to the decrease in the chance of 
getting echoes of high amplitude and 
long delay as the reverberation time 
approaches zero. It is believed that if 
the delayed echo problem were sepa- 
rately controlled, much higher values 
of reverberation time would be preferred. 



The last war brought the investigation 
to a standstill and, as the building of new 
theaters in England has been entirely 
suspended until such time as war-dam- 
aged housing is restored, we have had 
no opportunity of following a design 
from the drawing-board stage to the 
final pulse testing, but we have had con- 
siderable opportunity to compare pulse 
results with what we would predict from 
the plans of the theater. 

Let us consider just what we have 
found from pulse testing and how best to 
use that information in new designs of 
theaters. 

1. Good sound appears to be asso- 
ciated with a strong direct signal fol- 
lowed by a reasonable amount of low- 
level reflection to provide room color. 

2. The permissible intensity of a dis- 
crete reflection is approximately inversely 
proportional to the time it is delayed be- 
hind the direct sound. 

3. All discrete reflection should be re- 
duced by at least 20 db if it occurs more 
than 50 msec after the direct sound. 

4. The sound source and all early re- 
flections should subtend the minimum 
angle at the listening position. 

5. There should be no sharp changes 
in the acoustic impedance along the hall. 

As applied to the design at the draw- 
ing-board stage, it is advisable, first of 
all, to apply Sabine's or Eyring's equa- 
tion to correct the reverberation time in 
the normal way. When doubt exists, it 
is well to err on the side of making the 
reverberation time slightly lower than 
the present optimum. The reverbera- 
tion-time frequency characteristic should 
be controlled, the Knudsen-McNair 
relation being the best we can suggest, 
though we suspect that the "rise" called 
for at the bass end is somewhat excessive. 

Regarding theater-shape ratios, a 
width of 0.7 X length and a height of 
0.35 X length appear reasonable, though 
we regard this sort of data as a gross 
oversimplification of the problem, to be 
used only in the very first stages of design. 

Though the prewar British standard of 



152 



August 1951 Journal of the SMPTE Vol. 57 



aaa 




Fig. 7. General indication of preferred shape of theater. 



furnishing approximately 140 to 150 cu ft 
per seat has given satisfactory results, 
good results have been secured between 
120 and 180 cu ft per seat. 

When absorbent material has to be 
added to correct the reverberation time, 
we regard the ceiling as the least desir- 
able location. Energy flow between 
floor and ceiling is heavily attenuated 
by concentration of absorption on the 
floor, so that it appears desirable to 
confine any additional treatment to 
attenuating energy flow in the other 
modes. 

To secure good intimacy, we would 
suggest the following: 

1 . Concave surfaces should be avoided, 
particularly where they face the sound 
source. A concave back wall is par- 
ticularly harmful. 

2. Large flat surfaces should not be 
placed where high-intensity direct sound 
can fall upon them. Diffusion is gener- 
ally better than absorption, but regular 
patterns of simple diffusing surfaces 
should be avoided. Excess diffusion 
produces a characterless performance. 
The wall shapes should be such as to 
avoid echoes having a delay of more than 
60 msec occurring at any point within 
the seating area. 

3. A proscenium arch should be 
avoided and the cross section of the hall 
should change uniformly. 



4. Gangways and entrances should be 
placed against the sidewalk and not in 
the center of the theater, a position gen- 
erally containing some of the best listen- 
ing areas. (Figure 7 is a general indica- 
tion of the preferred shape.) 

It is appreciated that these suggestions 
may conflict with building, fire, or site 
restrictions, but they have been idealized 
as requirements to be approached as 
closely as circumstances permit. 

When considering cathode-ray tube 
methods of presenting acoustic data, it is 
dangerously easy to produce pictures 
containing so much information that they 
cannot be readily related to the results 
of subjective listening tests. The ear is 
almost insensitive to phase differences 
which produce large changes in a 
cathode-ray-tube picture. Because of 
this, and also because we are at the 
"crawling" stage in pulse analysis, it is 
necessary to present the simplest picture. 
This is met by radiating a pulse with the 
simplest possible frequency spectrum, a 
pulse of audio tone several cycles long. 
The frequency spectrum of a pulse of 
fixed length increases in complexity as 
the number of cycles in the pulse is re- 
duced, and there is, therefore, some point 
in using a pulse consisting of a fixed 
number of cycles. We have found, 
however, that this is not justified in view 
of the decreasing importance of the lower 



J. Moir: Acoustic Analysis 



153 




30msec 






20 msec 






46 msec 



Fig. 8. Changes that occur as the pulse length is increased 
from 10 to 46 msec. 




154 



Fig. 9. Test equipment by Messrs. Owen and Webb. 
August 1951 Journal of the SMPTE Vol. 57 



frequencies in controlling intimacy. This 
has led to our standardizing a pulse 
length of 10 to 20 msec. 

Other investigators have chosen to use 
short pulses generally produced by a 
spark discharge, but in our experience 
this presents so much information cover- 
ing such a wide frequency band that it 
defies analysis. 

As the pulse length is increased above 
20 msec, the pulse pictures tend to lose 
their simple character due to interference 
between pulse components that arrive at 
the microphone position by paths of 
differing length. Figure 8 is an example 
of the changes that occur as the pulse 
length is increased from 10 to 46 msec. 

Experience tends to indicate that our 
subjective assessment of sound quality is 
in good agreement with the results using 
a 10- to 20-msec pulse. 

While we are certain that pulse 
methods are a powerful new weapon in 
exploring an auditorium, we feel that 
there is still much to be done. At present 
there is insufficient mathematical back- 
ground and while we know that strong 
reflections have deleterious effects upon 
sound quality, we also know that a com- 
plete absence of reflection can lead to 
unsatisfactory results. The basic ques- 
tion "How much reflection do we want?" 
can be answered only in broad terms. 

Change in our viewpoint and require- 
ments during the investigation led to con- 
siderable modification in the test equip- 
ment. More recently, the equipment has 



been carefully rebuilt by Messrs. Owen 
and Webb as illustrated by Fig. 9, the 
complete equipment packing into two 
cases approximately 23 X 16 X 12 in. 
The basic principles remain as illustrated 
by Fig. 3. 

The pulse technique described was 
developed during 1937-1940 in close 
association with C. A. Mason and is 
more fully described in Reference 2, but 
a deeper realization of the significance 
of the pulse technique developed in the 
immediate postwar years. 

We are indebted to H. L. Webb for 
most of the experimental work and our 
thanks are due to the Directors of the 
British Thomson-Houston Co., Rugby, 
England, for permission to describe the 
results of the investigation. 

References 

1. See, for instance, Architectural Acoustics, 
V. O. Knudsen, Wiley, New York, 1932. 

2. C. A. Mason and J. Moir, "Acoustics of 
cinema auditoria," /. Inst. Elec. Engrs. 
(London), vol. 88, part III, pp. 175-190, 
Sept. 1941. 

3. J. Moir, "Reverberation time as an 
index of room performance," Report of 
the Physical Society (British) Acoustic 
Group Meeting, 1947, Physical Society, 
Prince Consort Gardens, Kensington, 
London. 

4. C. A. Mason, "Interpretation of pulse 
measurements," Report of the Physical 
Society (British) Acoustic Group Meet- 
ing, 1947, Physical Society, Prince 
Consort Gardens, Kensington, London. 



J. Moir: Acoustic Analysis 



155 



Notes on Movie Theater Acoustics 
in Scandinavia 



By UNO INGARD 



In the Scandinavian countries no fundamental or systematic research on 
acoustics in movie theaters has been done, as far as I know, and, as a non- 
authority in the field, I am able to give only a brief informal report of some 
facts about our theaters and what I think is the general opinion on theater 
design at the moment in Scandinavia. 



N. 



ATURALLY most of our theaters are 
rather small compared with the theaters 
in this country, seldom with as many as a 
thousand seats. The theaters are used 
only for moving pictures and not for 
other kinds of entertainment, so no 
attention has to be paid, in acoustic 
design, to such problems as organ music, 
for example. 

The general design data used, deter- 
mining the main dimensions of the 
theater, have been learned almost com- 
pletely from American experience, with 
slight modifications here and there. To 
mention some figures from the design 
data, we believe the volume per seat 
should be around 120 cu ft for theaters 
of ordinary size (about 500 seats). The 
relation between screen size and viewing 



Presented on June 7, 1949, as part of the 
Forum on Motion Picture Theater Acous- 
tics, sponsored by the SMPE Atlantic Coast 
Section and the Acoustical Society of 
America, held at New York, by Dr. Uno 
Ingard of Chalmers University, Gothen- 
burg, Sweden, and for the present year at 
the Acoustics Laboratory, 20B-052, Massa- 
chusetts Institute of Technology, Cam- 
bridge 39, Mass. 



distance tends in modern design to be 
kept below 5, although it lies between 5 
and 7 in most older theaters. Other 
dimensions, mainly determined by visual 
rather than acoustic conditions, are a 
ratio of 1 : 1.7 between width and length 
and 1 : 2.5 between height and width; 
numbers which I think are about the 
same as the average used in this country. 
The designers are well aware of the 
importance of avoiding echoes of all 
kinds. Considerable experience of that 
sort has been obtained from work of a 
corrective nature. One notable example 
of corrective design is the new radio 
house in Copenhagen in Denmark, 
where an unusual amount of work was 
done in order to obtain the most satis- 
factory acoustics in studios and music 
halls. One of the most obstinate prob- 
lems met in this work was the elimination 
of flutter echoes built up through mul- 
tiple reflections. Correction was accom- 
plished by changing the shapes of the 
rooms until the echoes were eliminated. 
This fact gives an example of the diffi- 
culty of predicting the appearance of 
flutter echoes or long-path echoes from 



156 



August 1951 Journal of the SMPTE Vol. 57 



two-dimensional geometrical analysis. 
The two-dimensional method, however, 
is used by most of the designers. A great 
improvement would be made if a three- 
dimensional simplified descriptive geo- 
metrical method could be developed. 

We have learned from Mr. Moir (see 
the preceding paper in this JOURNAL) of 
a method of studying the echoes in an 
existing building, but it would certainly 
also be nice to design an "instrument" 
for predicting the echoes, so they can be 
avoided from the time the building is in 
design. 

The shapes of the modern theaters are 
in most cases of the usual type, narrow in 
the front and wider in the rear part, with 
a strongly absorbing rear wall. In only 
two cases I know of, have modern thea- 
ters been built without absorption on 
the rear wall. In one of them, absorp- 
tion material was put up later in order 
to reduce disturbing reflections from the 
wall. The other case seems to have come 
out all right. It is the Alexandra Theater 
in Copenhagen, the rear wall of which 
was made sloping, in order to reflect the 
sound down to the rear seats. The side 
walls in this theater are also tilted, 7 
degrees inward, the reason being to get 
some of the sound reflected down to the 
floor instead of letting it go to the rear 
wall, where it might give rise to dis- 
turbing echoes of some kind. The re- 
verberation time in this theater is rather 
high, around 1.7 sec at 500 cycles, which 
is much higher than the average. A 
theater of the same shape but without 
balcony has been built in Stockholm, 
Sweden, but there absorption material 
was introduced both on the side walls 
and on the rear wall. Unfortunately, I 
have had the pleasure of visiting only the 
theater in Sweden, so I cannot make any 
statement of comparison. The tilted 
side walls have been used also for ordi- 
nary auditoriums; for example, the new 
physics lecture hall in Gothenburg. 

In regard to the shape of the room, it 
might be mentioned that the type of 
floor which is lowest in the middle is 



beginning to be used in motion picture 
theaters in Scandinavia. Because it is 
lowest in the middle and rises toward the 
rear and front parts of the theater, it is 
possible to eliminate some of the "neck- 
strain" for the spectators in the front 
seats and to make visual obstruction 
small and almost equal at all parts of 
the theater. 

Even if the volume per seat is kept 
low, and plane parallel walls, etc., are 
avoided to get good diffusion, a certain 
amount of absorbing material of some 
kind is usually introduced to keep the 
reverberation time low. As a basic 
criterion (besides that of uniform and 
sufficient sound intensity at all seats), 
we believe that the sound reproduced in 
the theater should be of the same quality 
as where the scene was taken, assuming 
that the sound on the film has the correct 
reverberation time to begin with. This 
criterion can, of course, be fulfilled only 
if the reverberation time is sufficiently 
low. This criterion is directly connected 
to the problem of reverberation time for 
electrically-coupled rooms. 

The problem is to find the resulting 
reverberation time in the reproduction 
room of a sound which is picked up in a 
sending room. The sending room and 
the reproduction room generally have 
different reverberation times. The com- 
bined reverberation time is approxi- 
mately equal to the longer of the two 
reverberation times of the sending and 
reproduction rooms. This is true if the 
separate reverberation times are not too 
close. If they are equal, the combined 
reverberation time in the reproduction 
room is 20% higher. It may be men- 
tioned that the reverberation curve is not 
an exponential function in this case, and 
that the reverberation time is taken as 
the time required for the intensity to 
reduce 60 do. If the reverberation is 
based on, for example, 40 db, the differ- 
ence mentioned above is larger than 20% 
which is also the case if the slope of the 
curve is taken as a base for the definition 
of reverberation time. 



U. Ingard: Theater Acoustics 



157 



As an illustration, let us assume that a 
scene has been taken out of doors, where 
the reverberation time is small. When 
reproducing this, we cannot get shorter 
reverberation time than that of the 
theater, which for low frequencies might 
go up to about 3 sec. The coordination 
between reverberation time and the 
picture shown on the screen under such 
conditions cannot be satisfactory. I 
don't know of any systematic studies of 
this problem, but it would certainly be 
interesting to learn how we react for a 
bad consistency of that kind. 

The advantage of a short reverbera- 
tion time is not limited to satisfying the 
criterion mentioned. There are other 
advantages, for example, the possibility 
of obtaining well-defined "sound focus." 
That this is of importance is established 
by the results from the survey made by 
Mason and Moir. In some cases, the 
theaters were reported unsatisfactory 
because of the confusing feeling resulting 
from bad sound focus. Good sound focus 
might be rather difficult to obtain with a 
large amount of reverberant energy 
present. Furthermore, and this may be 
most important, the possibilities of ob- 
taining disturbing echoes is much re- 
duced. Since we know that it is very 
difficult to avoid them in the original 



design, using ordinary design rules, ab- 
sorption seems to be the safest solution. 
Another advantage with high absorption 
is the improved reduction of noise, which 
I think is of importance. 

In order to fulfill the criterion men- 
tioned that the sound shall have the same 
quality as at the place where it was 
originally picked up, we must keep the 
reverberation time almost independent 
of frequency. By proper choice of ab- 
sorbers it should be possible to obtain a 
rather straight characteristic. 

The absorption material which is used 
in the theaters in Scandinavia is mainly 
thin-panel absorbers for low frequencies 
and some kind of porous absorber for the 
highs. The most usual type of porous 
absorber is tiles of wood fiber. Among 
the fireproof tiles can be mentioned 
asbestos and different kinds of gypsum 
constructions. A very nice method used 
frequently is asbestos spray. This is very 
expensive in our country compared with, 
for example, tiles of wood fiber. There 
is, however, a great demand for fire- 
proof tiles and I am surprised that tiles 
of glass fiber, such as used in this coun- 
try, have not yet been manufactured in 
Scandinavia. At the present time, when 
glass or rock wool is used, it is always in 
connection with perforated facings. 



158 



August 1951 Journal of the SMPTE Vol. 57 



Discussion on the Forum on 
Motion Picture Theater Acoustics 



Members of Discussion Panel: 

LEO L. BERANEK (Moderator), Massachusetts Institute of Technology 

JOHN E. VOLKMAN, RCA Victor 

JAMES Y. DUNBAR, William J. Scully, Inc. 

RICHARD H. BOLT, Massachusetts Institute of Technology 

EDWARD J. CONTENT, Acoustical Consultant 

A. W. COLLEDGE, Western Electric Company 

EDWARD S. SEELEY, Altec Service Corporation 

HARRY F. OLSON, RCA Laboratories 



Dr. Beranek: To start the discussion, I 
will call on those at the table, starting at 
the end: 

A. W. Colledge: Not having done any 
acoustic design work since the late '30's, 
I can take a more academic and historical 
viewpoint than some others here. 

If this problem were simply the acous- 
tical design of an auditorium, and speci- 
fically the theater auditorium, there 
wouldn't be the difference of opinion that 
may show up as this discussion gets under 
way. Our subject might better be de- 
fined as how to achieve excellently repro- 
duced speech and music in a theater 
auditorium with the restrictions imposed 
on us. We reproduce in the theater both 
speech and music from a sound track that 
reflects the acoustics of the sound stage 
and the electrical characteristics of the 
recording system, and is affected by the 
reproducing equipment in the theater. 

Also, in talking of the reverberation 
time of an auditorium, we will have to 
take into account the "apparent" rever- 
beration time. As an illustration of my 
point: if you take a long narrow room 



lined with tile, you will find that the 
acoustics are terrible. If you place loud- 
speakers in the ceiling, pointing down 
and operating at low levels, you will get 
quite good reproduction as far as the 
people seated in that room are concerned. 
So there is something, if you will, in 
"apparent" reverberation time. 

Before the discussion gets under way, I 
will stick my chin out and say that I feel 
we, as a group, have gone too far in try- 
ing to get too much "liveness" in an 
auditorium, that is, high reverberation 
time. I believe there are reasons for 
that, and probably I can point out some 
of them. 

Initially, our job was only to get repro- 
ducing equipment into the theaters. 
Then acoustics reared its ugly head, and 
several of the larger companies formed 
acoustic groups. There wasn't very 
much known about acoustics before then, 
and what was known was derived pri- 
marily from results obtained in a few 
theaters. But we suddenly had a few 
thousand theaters thrown at us. 

I still remember that those theaters, 
which are now considered overly dead. 



August 1951 Journal of the SMPTE Vol. 57 



159 



were the ones where the customers could 
sit in any seat, relax and understand the 
performance; and the problem of placing 
horns was quite simple. However, these 
theaters were few in number, the large 
majority were acoustically fair to poor, 
and something had to be done to them to 
obtain good reproduction. The only 
thing to do was to place absorbing ma- 
terial on the rear and side walls and rear 
ceiling, and you would get at least satis- 
factory results. 

About that time, we suggested tenta- 
tive reverberation standards and started 
experimenting with means of measuring 
reverberation times. We found that the 
calculated values did not always agree 
with the measured times. Also, we be- 
came conscious of the effects of shape and 
low-frequency absorption. We found 
that in theaters that had wood paneling 
we didn't get the "booming" effect of a 
high amount of low-frequency reverbera- 
tion, but instead got quite desirable 
sound. We began to suspect that a flat 
reverberation-frequency characteristic 
was something we would prefer. 

But as we got into the shape factors, we 
began to feel and I am afraid some 
hoped that with nonparallel and 
broken-up surfaces, we could stand 
greater reverberation times. Also, I 
think too much emphasis was placed 
upon the quality of music reproduction. 
It is generally agreed that the optimum 
reverberation times for speech and for 
music are quite far apart. And some- 
thing of which we have often lost sight is 
that about 80% or 90% of all sound com- 
ing out of Hollywood is speech. 

It seems to me, therefore, that in our 
consideration of the design of the acous- 
tics of a motion picture auditorium we 
should be guided by this fact in the com- 
promise that we must make in the rever- 
beration time. We must make this com- 
promise to get good speech reproduction. 
I feel that, for those theaters that hit such 
an average, the music reproduction is not 
at all objectionable. 

How far we have gone, I do not know. 



I am ashamed to say that I can't quote 
the Academy figures. I do remember, in 
one theater, using a value of reverbera- 
tion time of about 1 sec for a volume of 
1 00,000 cu ft. I admit it was not "live," 
but I don't think it was dead. We 
never had any complaints on sound 
quality ! 

If we have gone too far toward high 
reverberation times, I think that, as I 
said before, one of the reasons was the 
hope that complete breakup of surfaces 
would allow us to tolerate greater "live- 
ness." It is possible, too, that during the 
period when higher reverberation times 
came into use, we made a lot of measure- 
ments using a number of horns which 
were quite directional in the frequency 
range above several thousand cycles. 
That is why I introduced the term "appar- 
ent liveness." I think it is quite obvious 
that if we placed the reproducing horns 
high above the stage and pointed them 
down into the audience, we had a mini- 
mum of side-wall reflections, no ceiling 
reflections, and those reflections we did 
get were relatively short. Under these 
circumstances, we judged that we could 
tolerate more "liveness." Subsequent to 
those tests, multiple horns were intro- 
duced to give us a dispersion of high fre- 
quencies, and the side walls are now back 
in the picture. There is now a sus- 
picion, at least, that we have gone too far 
down the trail of "liveness." 

Dr. Richard H. Bolt: I am very glad 
that Art Colledge took the academic 
point of view. That leaves me free to be 
quite unacademic. I find that I am in 
substantial agreement with virtually 
every point that has been made. Per- 
haps this isn't a healthy situation for a 
discussion. I would like, therefore, to 
pick up just two or three of the points 
which Mr. Moir and Mr. Ingard have 
made, and toss out a few comments re- 
garding them. 

This question of the first 30-db decay 
being important is certainly logical, espe- 
cially when you take Mr. Colledge's 



160 



August 1951 Journal of the SMPTE Vol.57 



statement that some 90% of footage is 
speech, and when you add to that the fact 
that the speech articulation area has a 
30-db dynamic range. In no case can a 
speech component interfere with intelli- 
gibility after it has decayed 30-db. 
Some number such as this seems to make 
sense in the case of speech. Perhaps it 
also makes sense in the case of music, 
though we aren't yet established on a 
music-articulation engineering curve, as 
we are on speech intelligibility. 

Another interesting point is that this 
curve of the combined reverberation from 
two rooms of equal or different reverber- 
ation times is quite suggestive. It starts 
out, as Mr. Ingard pointed out, with a 
rather small slope, smaller than the final 
slope. 

Now, if again we take just the first 20 
or 30 db of the decay, obviously we are 
talking about a longer "reverberation 
time," as Mr. Moir implied, than the 
value defined for 60-db decay. 

I believe others have experienced what 
we have, namely, that when viewing a 
movie playback, which was originally re- 
corded under one condition of reverber- 
ation and played back in a room with a 
different reverberation time, and when 
you know roughly what these two rever- 
beration times are, and go through the 
calculation which Mr. Ingard suggested, 
you usually get the impression that the 
combined reverberation is a good bit 
higher than would be expected from the 
simple calculation of the combined rever- 
beration from two coupled rooms. 
Many times it seems more than 20% 
higher. This feeling, I think, is asso- 
ciated with the first part of the curve. 
These things all seem to make sense. 

I did have one question I wanted to ask 
Mr. Colledge. When he was discussing 
the low-level multiple loudspeaker sys- 
tem and mentioned that he got good re- 
production, I presume he was referring 
to the good speech intelligibility, and not 
necessarily good presence. 

Mr. Colledge: That is right. 

Dr. Bolt: One of Mr. Moir's points was 



an interesting one: that there should be 
no sharp changes in acoustic impedance 
as you go down the hall. Intuitively, 
this certainly seems reasonable to me, but 
I don't quite visualize it in a quantitative 
way, and I wonder if you have further 
comments to explain just what you 
meant? Also, I have another question: 
You suggest no proscenium arch, and I 
wonder what led you to make that sug- 
gestion. 

Also, I would like to support the state- 
ments and implications of both Mr. Moir 
and Mr. Ingard, that the question of pro- 
portions for relatively large theaters is 
probably more a matter of design and 
pleasing proportions, than of achieving 
some of the other factors we are looking 
for. Of course, if with proportions of the 
"recommended" type we can do a better 
job of distribution or of avoiding too long 
delayed echoes, that is fine. The point 
I wish to bring out here is that in rooms of 
more than 10,000 or 20,000 cu ft, it does 
not make sense to talk about the room 
proportions as providing a smoother dis- 
tribution of normal frequencies. At low 
frequencies, in rooms of below 10,000 or 
20,000 cu ft, and in small, strictly rec- 
tangular rooms, this has meaning. But it 
is hard to see how it has importance in 
rooms of 100,000 cu ft. 

I would like to conclude with a thought 
I picked up when I referred back to 
"home base" on this question of acous- 
tics. That is a healthy thing to do, occa- 
sionally: to forget about technical details 
and check with a somewhat impartial 
observer: my severest critic who has ac- 
companied me to many theaters. I asked 
what she thought of the acoustics in a 
particular theater which I had a hand in 
designing. She had only one comment. 

I might point out that her special inter- 
est was dramatics. She taught it, and 
acted it a good bit, and was quite familiar 
with the stage. She said, "Don't you 
realize that movie technique is different 
from the legitimate theater technique! 
A good actor on the stage times his 
speeches to the audience reaction. Now, 



Theater Acoustics Forum 



161 



if he finds that a certain punch-line is 
drawing an unusual laugh, he waits for 
the laughter to die down, and then goes 
on with his next speech. On the other 
hand, if you try, in the movies, to design 
the sequences for the most enthusiastic 
audience, you will occasionally get a dud 
of an audience and there will be some 
gaping holes in the speech. So you have 
to compromise." She said, "It is true 
that to some extent this question of audi- 
ence reaction is built into good movie 
dialogue, generally by having the punch- 
line followed by something unimportant. 
But this isn't carried out 100% in movie 
technique." 

Now, this suggests that audience noise 
is a good deal more important in a movie 
theater than in a legitimate theater. I 
support the thought that, by reducing re- 
verberation time, we gain on this point 
of noise reduction, as well as on several 
others that have been brought out. 

However, I am not quite convinced 
that zero reverberation would be good. 
So far as the quantity, or the magnitude, 
of reverberation time is concerned, we 
will agree that combining two rooms pro- 
duces some such predictable reverber- 
ation time. But suppose you are sitting 
in a dead hall and looking at a picture 
which is in a reverberant space, so that 
you expect a lot of reverberation. 
Maybe it is a politician in a huge con- 
vention hall, giving an address, and you 
record a lot of reverberation. But, if the 
film or sound is reproduced in the non- 
reverberant room, all of that reverberant 
sound is beaming at you from one point. 
Even though the recorded reverberation 
time is that which you expect, the effect 
of that reverberant sound, all coming 
from one point, is not necessarily the same 
as if the reverberant sound enveloped you 
completely. 

So you have this conflict, that, for sev- 
eral reasons, we apparently want lower 
reverberation times than we are used to, 
though I don't think we want it at zero. 
Perhaps we should get our absorption by 
highly concentrated, high-absorption 



areas, leaving some reflective surfaces all 
around the room. Then when rever- 
berant sound comes over the sound sys- 
tem, we can feel that some of it is indeed 
around us, and yet keep the reverberation 
time low enough for other requirements. 

Dr. Beranek: I think we should have 
Mr. Dunbar speak now and save Dr. 
Bolt's questions until later. 

J. T. Dunbar: Although much is al- 
ready known about the simple funda- 
mentals of the acoustics of theaters, I 
have, during the last six months, encoun- 
tered a number of theaters and auditor- 
iums, designed by well-known architects, 
that hark back to exactly what we are 
sitting under here the curved ceilings 
and concave back walls. There is no 
reason for such design in this country be- 
cause we have no fire regulations that re- 
quire it. Theaters are still being as 
badly designed, acoustically, as possible. 
Recently, I ran into one that seemed to be 
deliberately misdesigned. The curva- 
ture was exactly right to focus the sound 
into the middle of the audience. 
[Laughter] I have also seen theaters in 
which the balcony extended so far out 
and so deep that the absorption under- 
neath it made it impossible to hear in the 
back, even though there was no acoustical 
treatment under the balcony. 

I very much appreciate Mr. Moir's at- 
tempt here to evaluate scientifically the 
contribution of a hall to aesthetics, that 
is, to the resonance and the timbre of 
sounds produced in it. I do think that 
for best response to music, particularly, 
the hall should contribute a certain 
amount of quality to what is played in it. 
I believe that the hall itself is an exten- 
sion of the musical instruments in the 
hall, and that it adds to the timbre and 
resonance of the movie. It is rather a 
difficult thing to evaluate, but I think it 
would be a very good approach to try to 
find out what that contribution is. 

I would further like to accentuate Mr. 
Colledge's plea for deader halls or thea- 



162 



August 1951 Journal of the SMPTE Vol.57 



ters. In the first place, it means that re- 
verberation is changed very little by 
changing audiences. The lower the re- 
verberation is when the theater is empty, 
the less it is going to be changed by add- 
ing an audience to it; but if you start out 
with a high reverberation time, and some 
of these tests may have been made either 
in empty halls or partly-occupied halls, 
you get an entirely different response 
than you would if you had a full auditor- 
ium. If the change in reverberation 
time is very great, you have a hall that is 
very bad when there are few people in it, 
say, at the first show, and excellent at the 
next show. You get a minimum change 
in reverberation time with occupancy 
when perforated seat bottoms are used for 
sound absorption, or when heavily up- 
holstered seats are used, as in a few of the 
smaller theaters around the country. 

There is one playhouse in New Jersey 
where the seats are extremely well 
padded. That is an excellent idea be- 
cause you can take a nap if the show is 
dull. [Laughter] In that theater the 
reverberation is the same whether the 
house is full or empty. 

Another important consideration is the 
number of cubic feet per person. This 
number is a function of the number of 
people entertaining or talking. For ex- 
ample, the smoker in a Pullman car is 
roughly 6 by 8 feet in area and is a beau- 
tiful setting for the raconteur. In a lec- 
ture hall that holds up to 50 people, you 
must provide 70 to 80 cu ft per person. 
For larger-volume rooms the number of 
cu ft per person becomes much larger. 

The other question is the matter of 
height. If you increase the volume by 
increasing the height of the room, you 
aggravate your reverberation problem; 
and if you make it too low, then the sound 
doesn't distribute well in the back and you 
get peculiar reverberation effects. The 
ratios of width to length and height of a 
room are a function of custom that has 
come down through the ages from the de- 
velopment of public buildings that were 
more or less pleasing in shape and useful- 



ness. Hence, when we do something 
peculiar, it shows up immediately. 

Edward S. Seeley: I would like to em- 
phasize that we are here challenging the 
existing recommendations of optimum 
reverberation time. So far as I know, 
this is the first time that the established 
published recommendations have been 
challenged certainly the first time since 
the war, and perhaps since some little 
time before the war. 

I believe that out of this meeting will 
come a careful reconsideration of the 
whole question of reverberation time. 
Certainly it will have to be based upon a 
great deal of experienced discussion and 
comment from a large cross section of 
people interested in this subject. Noth- 
ing is going to be settled here this after- 
noon, I am sure, except that some of us 
will have convictions renewed, and a few 
may leave with convictions shaken. I 
have a feeling that although thinking in 
architectural acoustics has expanded 
rapidly in a lot of byways, it is still very 
strongly dominated by some of the very 
early conclusions. 

One of them, which I will come back to 
in a moment, is the definition of rever- 
beration time, which has existed un- 
changed for many years, but which is now 
being slightly restated. Although people 
haven't been following the concept of 60 
db of decay too closely, they have kept 
their eyes on that earlier definition, more 
or less. In most cases, you can't meas- 
ure more than 30 db of decay outside of 
the laboratory, and it is doubtful that the 
ear hears more than the first. I will 
come back to that in a moment. 

Another thing is that the original estab- 
lishment of optimum reverberation time 
for rooms was based on unamplified 
speech. The reverberation time per se 
hurts articulation. However, if the re- 
verberation time of a room is very low 
and the room is very large, the level of 
speech will be so low that unamplified 
speech will be unintelligible in the pres- 
ence of audience background noise. 



Theater Acoustics Forum 



163 



Nowadays, we have audio amplifying 
systems in every large hall, and I question 
seriously whether this change in the situ- 
ation has been adequately reflected in 
practice and in the recommended stand- 
ards. 

I might observe that my own connec- 
tion is with theaters that are operating 
thousands of them, of all kinds. We do 
not design or treat theaters, but we re- 
ceive their complaints of bad quality. 

I would emphasize that complaints are 
very rare where the house is too dead. 
Most of the complaints of poor clarity 
arise in houses which are on the rever- 
berant side, assuming, of course, that the 
sound system is not at fault. 

I would like to congratulate Mr. Moir 
and his colleagues in reducing to an engi- 
neering basis some of the things we have 
tried to handle by intuition, "golden 
ear" experting. 

Some of Mr. Moir's illustrations re- 
mind me of the significance of direct 
sound. We recognize the importance 
of direct sound in theaters, but very little 
may be found on this subject in the acous- 
tics books. In the theater, as one moves 
out of the area covered by the speaker 
the direct sound area quality drops 
rapidly, although the reverberation time 
is much the same. The ratio of direct to 
reverberant sound is tremendously im- 
portant when we are listening to speech. 

I am happy that a question has been 
raised concerning the extent of decay to 
be represented in an appraisal of the re- 
verberation time. In 1940 and 1941 I 
tried to sell the idea that we were too 
interested in the lower end of a decay 
characteristic. I would like to go further 
than the gentleman who preceded me 
and suggest that conclusions be based on 
the first 1 4 to 24 db of decay. I would be 
willing to consider favorably even less 
than 14 db as I question that trouble is 
very often experienced with sound that 
has decayed further than that. I have 
no evidence to back that up, other than 
personal observation. 



Dr. H. F. Olson: From the foregoing 
papers and the discussion, it seems that 
the ratio of direct to reflected sound ap- 
pears to be the important characteristic 
in sound motion picture theaters. 
Fundamentally, this becomes what we 
might call the effective reverberation, or 
as Mr. Colledge said, the apparent rever- 
beration. 

There appear to be several ways of ob- 
taining a suitable effective reverberation 
through proper design of the theater. 
Of course, the shape of the theater is 
involved, and that is a very complex sub- 
ject, as has been discussed here this after- 
noon. The effective reverberation also 
depends upon the reverberation time of 
the theater as well as other effects which 
are more complex and difficult to take 
into account. 

A proper effective reverberation can 
also be obtained by suitably designed re- 
producing equipment. For example, the 
effective reverberation depends upon the 
directivity pattern of the loudspeakers 
and the shape of the response-frequency 
characteristic. Thus, some engineers 
may work on the theater, others on the 
equipment, yet both obtain almost the 
same end results. It is quite true that 
you can have a very poor theater, yet can 
obtain very good sound reproduction by 
the use of suitable equipment. On the 
other hand, you can have only fair equip- 
ment, but a very good theater, and obtain 
very good sound reproduction. 

There is also one other type of theater 
which is very interesting, namely, the 
drive-in theater where the reverberation 
time is very low. In the drive-in theater, 
the accepted method is to use a separate 
loudspeaker for each automobile. The 
reverberation time of an automobile is 
very low. This system has brought 
many comments from listeners stating 
that they feel this type of reproduction is 
superior to that of the conventional en- 
closed theater. We have had similar 
comments from people about automobile 
radio receivers. Since the war, auto- 
mobile radios have been improved tre- 



164 



August 1951 Journal of the SMPTE Vol. 57 



mcndously, and people tell us that the re- 
production in automobiles is far superior 
to that which is obtained in the home. 
I believe that the improvement is due to 
both the characteristics of the receiver as 
well as the acoustical characteristics of 
the automobile itself. 

From what we have heard today, it 
seems that the subject of reproduction of 
sound is still a pretty complex one ! 



John E. Volkman: I, too, have been 
very much impressed by the engineering 
phase of Mr. Moir's paper. It gives a 
much better way, I believe, of going into 
the theater and finding out about those 
acoustical problems which we all admit 
have been present, but which we haven't 
been able to analyze well. In a nutshell, 
I believe that much of the data he has 
shown emphasizes the fact that echo is as 
disturbing in the theater as is general 
reverberation. 

What do Mr. Moir's results mean to 
the architect, and to the person who is 
going to build the theater? I think this 
forum emphasizes, as have a number of 
other forums, that there are still some 
very important acoustical problems that 
exist in theaters and that a lot of these 
problems are echo problems. These 
echoes arise from a curved rear wall, large 
expanses of flat areas, flutter echoes, and 
so on. 

Of course, in the sound movie theater, 
we can eliminate a lot of the echo prob- 
lems by speaker placement, and by mak- 
ing the speaker directional. If we can 
get the sound to travel directly to the 
audience without the beneficial aid of the 
side walls, so much the better. But no 
speakers have been designed yet which 
are so perfectly patterned that they de- 
liver sound only to the audience. 

In analyzing the sound arriving at the 
listener's ear, we have first the direct 
sound. Then we have the first and bene- 
ficial reflections. These are the ones 
that, as Mr. Moir indicated, come within 
the first 100 msec. 



Beyond that time, come reflections 
which are, perhaps, second or third re- 
flections. These are the disturbing echo 
reflections. After that there are the con- 
glomerate reflections which we think of 
mostly as reverberant sound in the room. 
The first 30 db of the decay portion of 
the curve concerns itself with those early 
reflections. In this country statements 
have been made that it is desirable to 
have the early part of the decay curve 
drop suddenly, and then the trailing-out 
reverberation will not be too disturbing 
from an articulation standpoint, but will 
add color to the overall sound. 

I would like to make a comment also 
with regard to the reverberation as per- 
ceived by the ear when there is a high 
noise level. In industrial plants, we have 
observed that with the noise in the plants 
we are not conscious of reverberation in 
the overall system. The same applies in 
those types of systems that have the 
multiple-speaker arrangement, which 
Mr. Colledge mentioned. However, if 
you stop the machinery and then listen 
to the sound, the reverberation sounds 
terrific; but you are not conscious of it 
when there is intense noise. So I think 
we are all agreed that those last reflec- 
tions that are more than 30 db down, are 
not of prime importance. 

There has been some discussion as to 
whether our optimum reverberation time 
is right, too high or too low. I don't 
think we are going to change that very 
much. The ear will tolerate consider- 
able variation, but it dislikes some of these 
disturbing echoes that get to the audi- 
ence. 

I think I agree with the other speakers 
that the shape factor that is, the pro- 
portions in the large room is not dic- 
tated so much by the acoustics as by other 
more general considerations of appear- 
ance, and so on, because the eigen tones 
[natural frequencies] and the room reso- 
nance are very close together, and are not 
predominant at the higher frequencies. 



Theater Acoustics Forum 



165 



E. J. Content: I think we are up against 
the same old problem that we have been 
fighting for a number of years what is 
high-quality reproduction? Frequency 
response, we know, is only one factor. 
There are many other factors in the elec- 
tric system which have been pretty well 
licked by now, such as signal-to-noise 
ratios and distortion in the electrical cir- 
cuits. Those, I think, we can discount 
and take out of the picture entirely. 
However, the acoustical distortions are 
the ones that we are more interested in, 
and they consist mainly of echoes and 
interference patterns. 

Mr. Moir stated that the worst theater 
he had studied also had the best fre- 
quency characteristic. I am wondering 
what he meant when he said it had the 
best frequency characteristic. Do we 
know what frequency response the ear 
likes best to hear? I think it is high time 
that we or the Society of Motion Picture 
Engineers, or someone, begins some kind 
of studies in the psychology of ear-hearing 
to determine what the ear likes to hear. 

You can have a flat loudspeaker in a 
relatively large auditorium, and may 
find it sounds perfect; but if you put that 
same reproducer in a small room, it 
sounds as though there are too many high 
frequencies in its output. That, of 
course, is a function of the attenuation of 
sound in the air. When you have a 
large auditorium, where the mean free 
path is large, you have much greater at- 
tenuation of the higher frequencies, espe- 
cially in locations where the humidity is 
very low at times. 

Now, let us go back to frequency re- 
sponse of a room. The frequency re- 
sponse, or frequency characteristic of the 
room is determined by the absorption of 
the different sounds by two means: one, 
by the acoustical surfaces; and the other, 
by the attenuation through the air. For 
a small theater to have the same re- 
sponse, much more absorption of the 
higher tones is needed than for a large 
theater. I am talking of the 1000-seat 
house, as against a 3500-seat one, because 



the length of a mean free path is much 
greater in the large house. 

If the reflected tones from the room 
surfaces and the tones from the loud- 
speaker have been attenuated to such an 
extent that they don't represent the same 
true character of tone that the loud- 
speakers emit, naturally it is much more 
pleasant to listen to the loudspeakers 
without any reverberation. However, if 
the absorption of the theater can be ad- 
justed so that the reflected tones give you 
the same response as the original sound, 
considerably more reverberation can be 
tolerated than otherwise. That is one 
reason why, when you get out of the beam 
of a loudspeaker, the tone goes to pieces. 
It is because the absorbing surfaces do 
not reflect the same tones that are cast 
upon them; otherwise, you would get the 
same tone color reproduced. 



Dr. Beranek [after thanking the panel 
speakers] : Mr. Moir has, I think, at least 
three questions to answer. I have been 
keeping track of them. He is supposed 
to answer: Why no proscenium arch? 
Why no sharp changes in peaks? And 
what is the best sound system character- 
istic? 

Mr. Moir: The first two questions 
really cover two aspects of the same prob- 
lem, that of maintaining a smooth flow of 
sound energy along the hall. Experi- 
ence in many cinemas has indicated that 
changes in sound level and sound quality 
are often associated with sharp changes in 
the cross section of the hall, of which two 
examples are the proscenium arch and 
the stadium-type of design. While no 
quantitative data on the adverse effects 
are available, a typical example could be 
quoted. A legitimate theater of modern 
design was the subject of serious criticism 
on the score of lack of intelligibility, until 
an apron stage extending forward of the 
proscenium arch and over the orchestra 
was constructed. As an ordinary mem- 
ber of the audience, the speaker had on 
many occasions noted the improvement 



166 



August 1951 Journal of the SMPTE Vol.57 



in intelligibility as an actor moved down 
stage past the proscenium arch. 

Regarding the best sound system char- 
acteristic, I have checked my idea of 
"best" in many British theaters and 
found that it did not differ appreciably 
from the published American data. In 
particular, a roll-off above 2.5 to 3 kc has 
seemed essential for acceptability. Any- 
thing flat to 5 or 6 kc has been found 
intolerable. 

Dr. Beranek: Are there other questions 
for Mr. Moir or other discussion? 

Mr. Volkman: We have made some- 
what similar measurements in the overall 
acoustic response. Some of the installa- 
tions that sound good were measured by 
the warble-frequency method. Inciden- 
tally, one of the nice features of Mr. 
Moir's method of measurement is that it 
simulates the short-pulse effect of speech. 

Going back to this response, we have 
found that a flat response up to 3200 
cycles which tapers off about 12 db per 
octave is preferred. In recording, they 
more or less raise the overall acoustic re- 
sponse at the top end. 

Mr. Colledge: It is pretty close to the 
Academy curve. Has your experience 
indicated that for typical public address 
systems' sound reinforcement, you can 
use more highs? 

Mr. Volkman: Yes. 

Mr. Colledge: I find that on stereo- 
phonic systems I can run to 1000, and 
then start tapering off. 

Mr. Moir: The experience we had con- 
firms your experience there. 

Mr. Volkman: But this does not show, 
of course, what your method shows, that 
your direct response may be rising, and 
your reflected response falling. 

Mr. Moir: Our work on frequency 
characteristics has given results of the 
same kind. 

Anon: Mr. Seeley pointed out that 
we are here challenging the accepted 
techniques of theater design. In order 
to make a satisfactory challenge, we must 
cumulate a lot more experience. It 
seems worth while, therefore, to dissemi- 



nate among the group here, at least, some 
of the details of technique that you have 
worked out, so that we can benefit in 
getting experience of our own. A ques- 
tion that occurs to me is how do you 
avoid the transient that normally occurs 
when you turn a signal on and off? Do 
you have some control over that? 

Mr. Moir: It is a problem, but a 
double contact switch can be used to close 
the circuit through a resistance, and then 
to short out the resistance. 

Anon: Do you find that this mechani- 
cal arrangement is satisfactory? 

Mr. Moir: We have gone no further 
than trying this arrangement. There are 
two or three other more important prob- 
lems on which we are doing some work. 

Anon: On your pictures, I noticed 
there was no peak no initial pulse. Was 
that because the picture didn't show it, 
or was it because it wasn't there? 

Mr. Moir: Do you mean the click? 

Anon: Yes. 

Mr. Moir: No, there was no serious 
click on the picture. There is no reason 
why it should be above the noise level in 
the theater. If you listen to the pulse, 
there is a slight click, but it does not ap- 
pear to be appreciable. We think that 
it can be neglected. 

Anon: Do you have any idea about 
what could be used as a quantitative 
measure of the ratio of direct-to-re- 
verberating sound? Would you inte- 
grate the area under the reverberation 
curve up to a certain value of time? 

Mr. Moir: I don't really know. We 
haven't done enough work to make a 
definite statement. We haven't really 
had enough experience to formulate any 
definite proposals. That is a weakness 
of the position as it is at present. It 
needs to be figured, but just at the present 
time we are in a depression in England, 
and there is no money for development. 
It is regrettable. 

Anon: One other question: Have you 
tried varying the frequency of the test 
oscillator, more or less continuously? 

Mr. Moir: We have taken pictures of 



Theater Acoustics Forum 



167 



pulses of tone over the whole frequency 
range. 

Anon: What I meant was, do you get 
a continuous variation as the frequency 
is changed? 

Mr. Moir: One of the methods we de- 
veloped was to try to take frequency char- 
acteristics in a very short time, of the 
order of 0.1 or 0.2 sec, but it revealed 
nothing and we dropped it. 

Ben Schlanger:* As an architect, one 
point that bothers me today is that, in the 
case of a motion picture theater, we have 
a very special type of auditorium which is 
different from the theater, where there is 
simply no reinforcement, and also a 
theater where there might even be re- 
inforcement, such as a public address 
system. 

For many years, now, motion picture 
theaters have had sound reproduction 
that we might call commercially accept- 
able, but we are coming to a new age in 
motion picture theater experience, in 
which the dramatic impact is going to be 
the thing. In other words, we have to 
go beyond the point of what is just accept- 
able on such aspects as audibility, in- 
telligibility, and so on. 

What it all boils down to is this: Is it 
possible for the acoustical color that is 
added by the room itself to be completely 
discounted so that whatever effect was 
made in the production could be de- 
livered to the audience without colora- 
tion by the room? 

Will a dual system of horns be effec- 
tive one set, which may be behind the 
screen, for the dialogue, where reverber- 
ation isn't important and the other 
set scattered around the room where an 
effective reverberation is required to 
give, dramatically, the effect desired? 

As architects, we have always been 
told by the acoustical engineers that the 
shape of the room and the amount of re- 
verberation, and so forth, are important. 



* Partner, Schlanger and Hoff berg, Theater 
Engineering and Architecture Consultants, 
35 W. 53rd St., New York 19. 



I wonder if we aren't past that stage. I 
noted that Mr. Ingard said they are going 
to less than 5 in the relationship of the 
screen width to viewing distances. That 
is an important point. I can safely pre- 
dict that is true. It is going to go far 
below 5. I think people are going to sit 
closer to the picture. The picture is 
going to dominate your field of vision. 

I think we have a whole new set of 
principles to work on, because the mo- 
tion picture is no longer the novelty, at 
least the sound motion picture, that it was 
20 years ago. Today it is dramatic im- 
pact, size of picture and realistic delivery 
that have become important, because 
home television has become a real com- 
petitor. 

I have been very much interested in 
what was delivered here. I think you 
are really making progress, but I feel you 
have to give prime consideration to the 
ultimate aim, and that is more effective 
delivery of both the visual and aural 
storytelling. 

Mr. Moir: I think some of the engi- 
neers here might reply to these points 
better than I. I know of no method of 
giving you open-air experience in an 
enclosure, for various well-known rea- 
sons. I think you may be right when 
you say you should move along those 
lines, but I would like to tackle some of 
the problems that are easier than that. 

Mr. Seeley: I feel that the relationship 
you found between frequency character- 
istic and quality is an effect and not a 
cause, possibly. You probably selected 
frequency characteristics most successful 
in the house, and then you later made 
measurements and found out what those 
characteristics were. It does not mean 
that the characteristic that slopes off 
quickly or remotely is a good one, but is 
something that reflects some character- 
istic or quality of the house. 

Dr. Bolt: I don't believe that this 
point has been brought up as yet, but it 
certainly is an important one: the ques- 
tion of the proper adjustment of level in 
the theater. We had occasion recently 



168 



August 1951 Journal of the SMPTE Vol. 57 



to make measurements continually dur- 
ing the performances in a theater at vari- 
ous points, not only to listen, but to over- 
hear comments of people watching the 
show and the people who came out from 
the show. There was a relatively small 
level difference which separated good 
from bad. 

In this particular case, when we were 
running around an 80- to 85-db average, 
the reactions expressed after the show 
indicated that that was too loud. We 
had control over the level in this theater 
during the performance. When we got 
it down to about a 60-db average on the 
speech, we were missing a good bit of the 
intelligibility. Then we heard a conver- 
sation behind us, where a girl and a boy 
who were enjoying the show, said, "Gee, 
can you hear that very well? Something 
must be wrong." That was at 60. Be- 
tween 65 and 70 the level was satisfac- 
tory. 

The significant thing that came out of 
measurement of this kind was that not 
more than 15 db separates pretty bad 
from pretty good. I wonder if this is the 
sort of experience found by the others? 

Mr. Moir: Yes. The BBC published 
some figures on level preference tests. I 
have the papers in my bag and will show 
you the figures. They found, sur- 
prisingly, that the engineers preferred a 
higher level than the public, and older 
people preferred it slightly lower in level 
than young people. 

Mr. Volkman: You described the one 
case where the listening conditions were 
good in some parts of the auditorium, and 



poor in other parts. How highly local- 
ized were the poor listening areas in the 
theater? Do you have some information 
on that? 

The reason I ask is that we had a simi- 
lar problem in the Radio City Music 
Hall about ten years ago when we used 
frequency pulses to measure the echo and 
help us locate the echo. We found it to 
be due to the columns supporting the 
mezzanines just at the rear of the orches- 
tra seating area, and they had to be in- 
clined forward. The total area affected 
by those columns was very minor, and 
the echo was only in the rear of the audi- 
torium. When we inclined them, we got 
rid of it. How localized was that? 

Mr. Moir: In that case, I showed a 
slide. It was over 4 seats. 

W. F. Jordan:* It has been said that 
the acoustics problem must be carried all 
the way through to the recording. If I 
recall correctly, back when sound pic- 
tures first started, the recording char- 
acteristics were changed in a very radical 
manner, in order to adapt the sound to 
the then existing theater conditions. 
Now, as architectural improvements are 
made, we are going to have to revise our 
original concept of a recording character- 
istic. In other words, the so-called 
Academy characteristic, a large rise in 
the high-frequency response, may have to 
be modified. 

[Moderator Beranek adjourned the 
meeting.] 



* Movietonews, 
York 19, N.Y. 



460 W. 54th St., New 



Theater Acoustics Forum 



169 



New American Standard 

Sound Transmission of Theater Projection Screens, PH22.82, was developed 
by the Society's Sound Committee based on a war standard, Z52. 44-1 945. 
The specified transmission characteristics are in accord with most present- 
day theater screens of proven performance value. 

The need for this standard was indicated by the occasional installation 
of screens with excessive transmission loss. Increasing the gain of the 
sound system as a compensation very often drives the amplifier into its 
nonlinear region and consequently produces excessive distortion. 



170 August 1951 Journal of the SMPTE Vol. 57 



American Standard for 

Sound Transmission of pH22.82.i95i 

Perforated Projection Screens 



UDC 778.5544 



1. Sound Transmission Characteristics 

1.1 The sound transmission characteristics of perforated projection screens 
shall be such that the attenuation at 6000 cycles, with respect to 1000 cycles, 
is not more than 2Vz db and the attenuation at 10,000 cycles, with respect to 
1000 cycles, is not more than 4 db. The regularity of response shall be such 
that there is no variation greater than 1 db from a smooth curve at any 
frequency between 300 and 10,000 cycles. The general attenuation at and 
below 1000 cycles should be not greater than 1 db. 

2. Method of Measurement 

2.1 The sound transmission of the screen shall be measured by means of 
a loudspeaker, fed by an audio oscillator and amplifier, behind the screen, 
and a calibrated microphone, amplifier, and output meter in front of the 
screen. The loudspeaker shall be of the type normally used in motion picture 
theaters for the size of screen being tested, and shall be placed with its axis 
not less than 2 feet from an edge of the screen with its mouth parallel to and 
separated from the screen by 4 to 8 inches (center cell in the case of a curved- 
front multicellular horn). The microphone shall be located 10 to 12 feet in 
front of the screen and on the axis of the loudspeaker. The sound transmission 
of the screen at any frequency is then the difference in the sound level 
measured with the screen in place and with the screen removed. 

2.2 Suitable precautions shall be taken to eliminate or minimize the effect 
of standing waves in the test room. 



Approved July 17, 1951, by the American Standards Association, Incorporated 

Sponsor: Society ef Motion Picture and Television Engineers 'Universal Decimal classification 

Copyright, 1951, by American Standards Association, Inc.; reprinted by permission of the copyright holder. 

August 1951 Journal of the SMPTE Vol.57 171 



70th Convention 



Hollywood Roosevelt Hotel, Hollywood, Calif., October 15-19, 1951 



Color Processes of motion picture photog- 
raphy and release print- 
ing now being introduced commercially 
are capturing the interest of all motion 
picture producers and film laboratories. 
Latest developments along these lines will 
be presented for the first time at one of 
the eleven convention sessions. Related 
to these current indications of progress 
in the field of "color" is the continuing 
work of the SMPTE Color Committee 
which will be reported upon by Chairman 
H. H. Duerr. 

Color Aspects of television have been 
in the public eye recently 
and, in addition to popular concern for the 
future of commercial color television, there 
has been serious interest among technical 
people. Examples of the most pressing 
questions are requirements of studio 
conversion to color standards, and an 
estimate of those factors now apparent 
that will some day prove to have had a 
significant influence over long-term growth. 
Both will be discussed at length during 
another session, along with the description 
of a new system for reproducing a color 
television picture. 

Magnetic Recording equipment newly de- 
veloped for efficient 

re-recording of feature film sound as well 
as numerous improvements in equipment 
and production techniques will be reported 
upon over two technical sessions. 

High-Speed Photography as a tool in 
aircraft, guided 

missile and ballistics research will be the 
subject of one convention session. Another 



will include papers on new developments 
in cameras and on sound recording as a 
data gathering process. 

Stereo-Projection, much conjectured 
about, will be dis- 
cussed, demonstrated and explained. This 
session which is certain to interest motion 
picture people widely is scheduled to 
include reports by two SMPTE engineer- 
ing committees, one on Picture Flicker 
and one on Screen Brightness. 

Chairman of the Pacific Coast Section, 
C. R. Daily, is also Local Arrangements 
Chairman for the fall convention. This 
latter title gives him the pre-convention 
responsibility for lining up the three sessions 
to be held away from the Hotel and for the 
general supervision of all arrangements 
except in connection with ladies' program, 
papers, motion picture short subjects, 
luncheon and banquet. He will keep an 
eye on: 

Hotel Reservations and Transportation which 
Bill Kunzmann has assigned to Vaughn 
C. Shaner. 

Projection Facilities, at all four meeting 
places, Hollywood Roosevelt Hotel Blossom 
Room, Academy Award Theater, Republic 
Studio Scoring Stage and Columbia 
Square. Emery Huse, Eastman Kodak 
Company, will provide the 16-mm arc 
equipment for use at the hotel. Members 
of Los Angeles Projectionists Local 150 
will put the pictures on the screen. 

Public Address equipment and the re- 
corder used to take down technical discus- 
sion will be supplied by SMPTE head- 
quarters and operation will be supervised 
by E. W. Templin, Westrex Corporation. 



Engineering Activities 



Color The Color Committee, under 
the Chairmanship of Dr. Duerr, 
met in New York in mid-June. Most of 
the Committee's work is done by Sub- 
committees; therefore the meeting opened 
with reports of Subcommittee Chairmen: 



(a) Color Symposium Subcommittee: 
Lloyd Varden indicated that additional 
information is still required before editorial 
work on publication of all color-process 
data can begin. Both DuPont and 
Ansco have preferred assistance along 



172 



these lines, and a draft of the introductory 
report should be ready shortly. 

(b) Subcommittee on Projection Light 
Sources and Screens for Color Film: 
Ronald Bingham discussed the status of 
the several projects. A good deal of 
information has been acquired on the 
effect of theater projection practices upon 
color quality and a report will soon be 
available. Characteristics of projection 
screens are also under study and a report 
is now being prepared by Mr. Gillon. 

(c) Subcommittee on Spectral Energy 
Distribution of Photographic Illuminants: 
Monroe Sweet stated that the Subcom- 
mittee had met on March 9, 1951, and had 
agreed that the aim of this group was "to 
prepare a report of the history, present 
status and, if possible, a proposal for 
improved methods of determining, and 
technology for specifying, the spectral 
energy distribution of photographic illumi- 
nants, particularly those used for motion 
picture photography." While in an early 
stage, progress is being made on this 
project. 

Dr. Duerr then reported that a request 
had been received to standardize the color 
temperature for color films used with 
tungsten light sources. The technical and 
commercial aspects of this problem were 
discussed and it was agreed that this matter 
properly belongs within the scope of the 
Motion Picture Studio Lighting Committee 
as far as motion picture technique is con- 
cerned, and within the scope of the ASA 
Sectional Committee, PH22, as far as the 
amateur and professional color films are 
concerned. The Color Committee would 
provide assistance to the Studio Lighting 
Committee if needed. 

The Committee's part in the Society's 
Glossary project was the last point on 
the agenda. After much discussion, it 
was agreed to set up a preliminary sub- 
committee whose function would be merely 
to determine which terms should be in- 
cluded in the Glossary. When this is 
completed a more formal committee could 
be established to work on the definition 
of terms. 



Laboratory Practice At its last meet- 
ing during the 
69th Convention in New York, the Labora- 



tory Practice Committee took definite 
action on two projects: 

1. A Subcommittee to initiate a standard 
on laboratory review-room screen bright- 
ness is to be formed under the chairman- 
ship of Edward Cantor. 

2. It was agreed to ballot the entire 
Committee on the "Proposed American 
Standard for 16-Mm Optical Printer 
Aperture for Enlargement Printing to 
35-Mm." Gordon Chambers was com- 
mended by the group for his efforts in 
preparing the recommendations upon 
which the proposal is based. The ballot 
is now almost completed and in all likeli- 
hood will be approved and forwarded to the 
Standards Committee. 

Screen Brightness In accordance with 
ASA's procedure of 

periodically reviewing American Standards, 
the Screen Brightness Committee is now 
taking a letter ballot on "Review of 
American Standard Z22. 39-1 944, Screen 
Brightness for 35-Mm Motion Pictures." 
The Standard, as presently worded, applies 
to all theaters. Outdoor theaters rarely 
achieve the minimum value of screen 
brightness as set by the Standard, and so 
as a practical matter there has been some 
talk of limiting the Standard to indoor 
theaters. This question is included in the 
letter ballot. 

Standards For the last several months 
the Standards Committee 
has been balloting on a whole series of 
proposals; some, on the question of the 
approval of preliminary publication and 
others, whose preliminary consideration 
has been completed, on the question of 
submitting to ASA for processing as an 
American Standard. These are: 

Preliminary Publication 

Proposed Standard for Aperture Calibra- 
tion of Motion Picture Lenses. 

Submission to ASA 

1. Dimensions for Projection Lamps 
Medium Prefocus Ring Double-Contact 
Base-Up Type for 16- & 8-Mm Motion 
Picture Projectors, PH22.84. 

2. Dimensions for Projection Lamps 
Medium Prefocus Base-Down Type 
for 16- & 8-Mm Motion Picture Pro- 
jectors, PH22.85. 



173 



3. Splices for 1 6-Mm Motion Picture 
Films for Projection, PH22.24. 

4. Splices for 8-Mm Motion Picture 
Film, PH22.77. 

Recently Approved 

Preliminary Publication Proposed Stand- 
ard for Gutting & Perforating Dimensions 
for 35-Mm Film (to be published in a 
forthcoming issue). 

Submission to ASA Edge Numbering 
of 16-Mm Motion Picture Film, PH22.83, 
and 16-Mm Motion Picture Projection 
Reels, PH22.11. 



Television Studio Lighting The Televi- 
sion Studio 

Lighting Committee met on June 20th in 
New York City. Unfortunately, the at- 
tendance was so small that it was impossible 
to make decisions representative of the 
thinking of a cross section of the television 
industry. The Chairman, Mr. Richard 
Blount, noted that while it might be 
difficult for those members outside of 
New York to attend meetings, he would 
welcome their written comments which 
would be of considerable value in directing 
the thoughts of the Committee. 



New Members 



The following members have been added to the Society's rolls since those last published. 
The designations of grades are the same as those used in the 1950 Membership Directory. 



Honorary (H) 



Fellow (F) 



Active (M) 



Associate (A) 



Student (S) 



Aye, Thomas L., Radio Engineer, Henry 
J. Geist & Associates, Inc. Mail: 42 
Middle Neck Rd., Roslyn, Long Island, 

Barstow, John M., Telephone Engineer, 
Bell Telephone Laboratories. Mail: 
105 Intervale Rd., Mountain Lakes, 
NJ. (M) 

Barz, Helmut, Head, Rawstock and Print- 
ing, High Commissioner for Germany. 
Mail: Astallerstr. 15, Muenchen, Ger- 
many. (M) 

Bhate, Arvind G., Development Engineer, 
National Carbon Co. (India), Ltd., P.O. 
Box 21 70, Calcutta 1 , West Bengal. (M) 

Brown, Ho M., Chief Engineer, The 
Ballantyne Co. Mail: 1707 Davenport 
St., Omaha, Nebr. (M) 

Chodkowski, Stanley, New Inst. for Film 
and Television. Mail: 19 Goodyear 
Ave., Buffalo 11, N.Y. (S) 

Chyka, George W., Motion Picture 
Cameraman, KOTV Cameron Tele- 
vision. Mail: 1320 S. Boulder, Tulsa, 
Okla. (A) 

Cooper, Donald H., Engineer-In-Charge, 
National Broadcasting Co. Mail: 14 E. 
Mason Ave., Alexandria, Va. (A) 

Dickinson, Robert V. C., Recording Engi- 
neer, Telescriptions, Inc. Mail: Roome 
Rd., Towaco, N.J. (A) 

Fields, Louis, Photographic Technician, 
Institute for Medical Research. Mail: 
4024 Stone Canyon, Sherman Oaks, 
Calif. (A) 

Filipowsky, Richard F. J., Professor of 
Electronics, Head of Faculty, Madras 



Institute of Technology (MIT India), 
Chromepet, ChingelputDt., So. India (A) 

Frierson, Leland G., Vice-President, Ruth- 
rauff & Ryan, Inc. Mail: 108 E. 86 
St., New York 28, N.Y. (M) 

Frisbie, H. E., District Service Manager, 
RCA Service Co. Mail: 9215 Fernhill, 
Parma, Ohio. (M) 

Geist, Henry J., Sales Engineer & Consult- 
ant, Henry J. Geist & Associates, Inc. 
Mail: 196 5th St., Stamford, Conn. 
(M) 

Glasser, Donald W., Photographic & Re- 
production Technician, Westinghouse 
Research Laboratories. Mail: 853 In- 
wood St., Pittsburgh 8, Pa. (A) 

Haraughty, Lois E., Chemist, Eastman 
Kodak Co., 6706 Santa Monica Blvd., 
Hollywood, Calif. (A) 

Hayden, Edward J., Chief Electrician, 
Ace Film Laboratories, Inc. Mail: 120 
Linwood Ave., Bellmore, Long Island, 
N.Y. (A) 

Heidt, Horace, Producer, Director, Actor. 
Mail: 14155 Magnolia Blvd., Van Nuys, 
Calif. f (M) 

Kantrowitz, Philip, Electronics Engineer- 
ing Research Assistant, Microwave Re- 
search Laboratories. Mail: 2435 Frisby 
Ave., Bronx 61, N.Y. (A) 

Kapur, Jit L., University of Southern 
California. Mail: 1023 W. 36 St., Los 
Angeles, Calif. (S) 

Lankester, Christopher H., Technical 
Supervisor, United Nations. Mail: 144- 
79 Grand Central Pkwy., Jamaica 2, 
N.Y. (M) 



174 



LaSala, Frank A., Foreman, Cameraflex 
Corp. Mail: 185 Forbell St., Brooklyn, 
N.Y. (A) 

Madsen, Erik R., Chief Engineer, Bang & 
Olufsen Aktieselskab. Mail: Gimsing- 
h0je, Struer, Denmark. (M) 

Mayer, Allan, Engineer, General Precision 
Laboratory. Mail: 132 Huntville Rd., 
Katonah, N.Y. (M) 

Mayer, George H., Lighting Carbon Spe- 
cialist, National Carbon Div. Mail: 
6207 Park Lane, Dallas, Tex. (M) 

Nash, Charles Kevin, University of South- 
ern California. Mail: 800 Sunset Ave., 
Venice, Calif. (S) 

Pieroth, John Phillip, Jr., Photographer. 
Mail: 1609 Peach Court, Seattle, Wash. 
.(A) 

Richman, Donald, Television Engineer, 
Hazeltine Corp. Mail: 64-25F 186 
Lane, Fresh Meadows, N.Y. (M) 

Riebel, Fred, III, Supervisor, Motion Pic- 
ture Bureau, AEtna Life Affiliated Com- 
panies. Mail: 151 Farmington Ave., 
Hartford, Conn. (M) 

Rothschild, Richard S., Engineer, Allen 
B. Du Mont Laboratories, Inc. Mail: 
1 165 Park Ave., New York 28, N.Y. CA) 

Schwartz, Morton, Film Recording, RCA 
Victor Div. Mail: 698 West End Ave., 
New York 25, N.Y. (A) 

Sheldon, Stewart, President, Sheldon 
Theater Supply. Mail: 1415 Amberly 
Dr., Dayton, Ohio. (M) 

Sims, John M., Commercial Manager, 
Motion Picture Equipment, General 
Precision Laboratory, Inc. Mail: Man- 
ville La., Pleasantville, N.Y. (M) 

Spiller, Gino, University of Southern Cali- 
fornia. Mail: 71 3f W. 35 PL, Los 
Angeles 7, Calif. (S) 

Tall, Joel, Audio Engineer, Tape Editor, 



Columbia Broadcasting System. Mail: 
1594 Unionport Rd., New York 62, N.Y. 
(A) 

Tohill, James C., Quality Control Analyst, 
Du-Art Film Laboratories, Inc. Mail: 
37-42 64 St., Woodside, Long Island, 
N.Y. (M) 

Torp, Richard V., Photographer & Color 
Technician, Technicolor Motion Picture 
Corp., Research Dept., 6311 Romaine, 
Hollywood 38, Calif. (A) 

Wentker, Fred W., District Service Man- 
ager (Chicago District), RCA Service Co. 
Mail: 1505 Oak Ave., Evanston, 111. 
(M) 

White, Reginald A., Engineer, General 
Precision Laboratory, Inc. Mail: 94 
Park Rd., Deepwood, Chappaqua, N.Y. 
(A) 

CHANGE OF GRADE 

Ballantyne, Robert S., President, Ballan- 
tyne Co. Mail: 1707 Davenport St., 
Omaha, Nebr. (A) to (M) 

Mitchell, Wayne, Photography Instructor, 
Cinematographer, Audio- Visual Center, 
Miami University, Oxford, Ohio. (S) to 
(A) 

Montague, Henry B., Projection Engineer, 
EUCOM Motion Picture Service, Main- 
tenance & Supply Section, APO 807, 
c/o Postmaster, New York, N.Y. (A) to 
(M) 

DECEASED 

Hornstein, Joe, President, Joe Hornstein, 
Inc., 630 Ninth Ave., New York 19, N.Y. 
(A) 

Newell, David A., Recording Supervisor, 
Samuel Goldwyn Studios. Mail: 1156 
N. Poinsettia PI., Hollywood 46, Calif. 
(M) 




Arthur Schneider 




Donald Stern 

Donald Stern and Arthur Schneider in the early spring were elected next year's Chair- 
man and Secretary-Treasurer, respectively, of the Society's Student Chapter at the Uni- 
versity of Southern California. Photos are by courtesy of University Photographer, 
University of Southern California. 



175 



Carl Louis Gregory 




The full and active life of Carl Louis Greg- 
ory, pioneer cinematographer, came to an 
end at the age of 68, last March in Van 
Nuys, Calif., after a year's illness of arterio- 
sclerosis. 

The man who was to receive many 
honors, be granted many patents, to teach 
and lecture widely, to pioneer in many 
parts of the motion picture field, was born 
in Walnut, Kan., in 1 882. At the age of 1 1 
he was making his own first camera from a 
cigar box and spectacle lenses. He entered 
Ohio State University in 1899, became a 
graduate pharmacist in 1 902 and was grad- 
uated in 1904 with a B.Sc. in Chemistry. 
He earned money for his college courses by 
doing the photographic work for the college 
annual and biological photography for the 
medical and veterinary colleges. 

After college began a career which for 
many years was to bring some new activity 
every year, sometimes with every change of 
season : 

In mid-1904 he joined the Official Photo- 
graphic Dept. of the Louisiana Purchase 
Exposition and was in charge of various 
sections including one where up to 1200 
individual portraits were taken in a day, 
the airdrome section with airship, balloon 
and aerostatic work for newspapers and 
publicity, and the Quick Post Card Gal- 
leries which took photos and finished them 
in seven minutes. 

In 1905 he was taking views for post 



card and commercial reproductions in the 
Southwest and Old Mexico, with a studio 
at Monterrey, Nuevo Leon, Mexico. In 
the spring of 1906 he had a commercial 
photography gallery at San Antonio, Texas, 
in conjunction with the Mills Engraving 
Co., and was making wet-plate line and 
halftone negatives for Mills. During the 
summer of 1906 he was official photog- 
rapher for Manitou & Pikes Peak Ry. 
That winter he was in charge of the photo- 
graphic Laboratory of Dodd-Rogers Co., 
Cleveland, Ohio, doing amateur finishing, 
blue printing and commercial photog- 
raphy. 

In the spring of 1907 he was appointed 
photographer with the U.S. Geological 
Survey, doing chiefly wet-plate work but 
also lens and shutter testing and photo- 
micrographic work under polarized light. 
In 1908 he transferred to the U.S. Rec- 
lamation Service, having first to do with 
everything in the making and exhibition of 
lantern slides then taking, developing, 
printing, titling and assembling motion pic- 
tures of the Reclamation Service work. He 
was then also installing, wiring up and 
operating stereopticons and motion picture 
projection machines to accompany lec- 
turers. That year he lectured on color 
photography at George Washington Uni- 
versity and before the American Chemical 
Society. 

In the winter of 1908-9 he was stage 
manager and photographer for Burr 
Mclntosh who gave lectures on "Our 
Country," "Our Navy," "Our Island 
Possessions, " etc., in the major cities of 
eastern United States. In the spring of 
1909 he began photographic investigation 
in cinematography for Thomas A. Edison. 

In 1910 he became Chief Photographer 
for the Thanhouser Film Co. and in 1911 - 
12 built for Thanhouser the California 
Studio which was later used by Majestic, 
Reliance and Chaplin film companies. In 
1912 he was chief photographer and often 
director of a large number of scenic, edu- 
cational, dramatic and propaganda films. 
In 1913 he was in charge of the entire pro- 
duction of the Princess Brand Films for 
Thanhouser, combining direction and 
photography of such films as Break Upon the 
Waters, The Little Church Around the Corner, 



176 



Her Right to Happiness, The Tangled Cat, 
Friday the Thirteenth, Her Way, A Shotgun 
Cupid, The Grand Passion, The Strike, The 
Campaign Manageress, The Mystery oj the 
Haunted Hotel, The Water Cure, A Deep Sea 
Liar, Little Brother, and many others featur- 
ing such stars as William Russell, Florence 
LaBadie, James Gruze, Margaret Snow, 
Muriel Ostrich, Mignon Anderson and 
John Lehnberg. 

He was the cameraman on the first serial, 
Million Dollar Mystery, starring Margaret 
Snow. 

In the winter of 1914 he was Chief 
Photographer for the Williamson Sub- 
marine Expedition to the West Indies. On 
that expedition he made the first motion 
pictures ever taken beneath the surface of 
the ocean, something which was a large 
factor in his being made a Fellow of the 
Royal Photographic Society of Great 
Britain in 1915. 

In the summer after returning from the 
West Indies he took a troop of actors on a 
western trip making dramatic and scenic 
pictures in the national parks under the 
permission and indorsement of the Secre- 
tary of the Interior. That fall he lectured 
at the Smithsonian Institution, Museum of 
Natural History at New York, the Philo- 
sophical Society at Philadelphia, and 
others. 

In 1915 he was engaged in photographic 
research for Technicolor with Prof. E. J. 
Wall at Massachusetts Institute of Tech- 
nology, then in the years 1916 and 1917 
successively was Chief Photographer for 
Henry W. Savage Motion Picture Produc- 
tions and Annette Kellerman Co., Fox 
Pictures. In 1918 he was in charge of in- 
struction at the U.S. Signal Corps School 
of Cinematography where 800 men were 
trained for overseas photographic units. 
In 1919 he was lecturing on photoplay mak- 
ing at Columbia University. Over 200 
reels of instructional film were produced by 
him in 1920-21 for the Graphic Instructor, 
subsidiary of United Publishing Co. which 
used the films for department store training. 



During the next year he was doing photo- 
graphic and research work for the Rodman 
Wanamaker Indian Foundation and pro- 
ducing such films as The Vanishing American, 
Marshal Foch's Visit to America and Indian 
Customs. In 1922-23 he was Managing 
Director of the Orient and India Picture 
Corp., producing films from his own scen- 
arios in the South Seas, Japan, China, 
Malaya, Burma and India. In 1924-28 
he was Dean of the New York Institute of 
Photography, during which he wrote one of 
his books on motion picture photography 
which is now reported on the rare book 
lists. In 1928 he was technical correspon- 
dent and in charge of professional equip- 
ment sales for Bell & Howell. From 1929 
until 1936 he was occupied as consultant 
on photographic and cine processes and pat- 
ents, serving such clients as Terrytoons, 
Fox, Pathescope, Metro, Paramount, Uni- 
versal, Eastman Kodak, Raycol of London, 
Societe Francais Cinechromatique of Paris, 
and Siemens & Halske of Berlin, holders of 
patents on the lenticular film color process 
which the Kislyn Corp. has owned in this 
country. In 1936 he became Assistant in 
charge of Motion Picture, Photographic 
and Sound Record Surveys at the National 
Archives in Washington, D.C., where he 
remained until 1946. 

He was a member of this Society and was 
also a member of the American Society of 
Cinematographers, the Edison Pioneers 
and the Oval Table Society. He was 
credited with building the first optical 
printer and he designed many machines 
such as a combined micro-colorimeter and 
densitometer, disk recording machine, a 
machine for cleaning dirty or oily film, for 
color processes as well as for cartoon ani- 
mation on which he had patents. He had 
been a frequent contributor to this Journal, 
as well as to many other periodicals. He 
had for several years been editor of the 
department "Motion Picture Photography" 
in Moving Picture World and had also for 
years edited "Amateur Cinematography" 
in Camera Magazine. 



SMPTE Officers and Committees: The roster of Society Officers and the 
Committee Chairmen and Members were Published in the April Journal. 



177 




Fred Schmid 



After 53 years of service with the G. P. 
Goerz American Optical Co., New York, 
President and General Manager Fred 
Schmid has resigned from active work and 
is now living in retirement at his home in 
Larchmont, N.Y. 

It was on September 13, 1898, when 
Fred Schmid's destiny was tied up with the 
Goerz interests. On that day, Fred 
Schmid, a young instrument-maker, 
applied for a position with the Goerz 
Optical Works in Berlin-Friedenau, Ger- 



many. After a few hours' interview with 
G. P. Goerz, the founder of the Goerz 
enterprises, the latter offered to send him to 
America to open a branch factory there, in 
order to meet the ever increasing demand 
for Goerz photographic lenses in the U.S.A. 
In a spirit of adventure young Schmid 
accepted the offer readily and, after six 
months of intensive study of the manufac- 
turing methods of the parent house, he 
arrived in New York in May 1899 to set up 
shop. Since then the making of Goerz 
American photo-lenses was carried on here 
under his personal supervision. 

The American firm was incorporated in 
1906 as the G. P. Goerz American Optical 
Company and its assets and manufacturing 
rights were acquired through purchase by a 
small group of American citizens in 1920. 
The German Goerz Company was merged in 
1926 with the well-known Zeiss Ikon Corp. 
in Germany. Today the American Goerz 
firm is the only company which supplies a 
full line of the Goerz Photo-lenses. 

Fred Schmid, at first in charge of pro- 
duction, was made General Manager in 
1910, Vice-President of the American com- 
pany in 1920 and finally President in 1937. 
He made the last of his frequent business 
trips back to Germany during the summer 
of 1949. The company has announced 
that Mr. Schmid will continue to serve on 
its Board of Directors and in a consulting 
capacity. 

Fred Schmid was born at Lehe, near 
Bremerhaven, on August 5, 1870, and next 
month will celebrate his 81st birthday with 
his three daughters at their summer cottage 
in South Salem, N.Y. He has been a 
member of this Society since 1929. 



BOOK REVIEWS 



Encyclopedia on Cathode-Ray 
Oscilloscopes and Their Uses 

By John F. Rider and Seymour D. Uslan. 
Published (1950) by John F. Rider Pub- 
lisher, Inc., 480 Canal St., New York 13. 
992 pp. + 8 pp. index + 3000 diagrams 
and illustrations. S [ / 2 X 11 in. Price 
$9.00. 

This valuable new book is a rather com- 
plete collection of practical information 
relating to modern oscillographs and their 



uses. There is the absolute minimum of 
mathematics included, and the authors 
have not resorted to too intense theoretical 
treatment. Only the essentials have been 
covered. Since the book is on a practical 
level it will undoubtedly find widespread 
acceptance. 

The reader will find a description of 
practically every type of commercial 
oscillographic equipment included, to- 
gether with information which the engi- 
neer can put to practical use every day. 



178 



As a matter of fact, there are 331 pp. 
devoted exclusively to instruments and 
accessory equipment. This rather com- 
plete coverage, in itself, will make the book 
extremely useful. 

Cathode-ray tubes are fully covered in 
some 171 pp. Over 200 pp. are devoted to 
specific applications of oscillographs, and 
107 pp. to circuit diagrams and various 
operating specifications. There is a com- 
plete bibliography at the conclusion of each 
chapter which will prove very valuable to 
the engineer for reference purposes. 

The 1580 illustrations showing photo- 
graphic reproductions of various wave- 
forms will unquestionably prove very valu- 
able to the average engineer, and the re- 
viewer finds the collection one of the most 
comprehensive to be found anywhere in the 
literature. 

It is regrettable that the word oscillo- 
graph has not been used instead of the 
term oscilloscope. The former is the more 
erudite term of the two and is undoubtedly 
to be preferred in scientific literature. 
Surely, the term oscillograph was the first 
word applied to the particular instrument, 
and an investigation of early writers on the 
subject will disclose its preference over all 
other terms. It was used, for instance, by 
J. B. Johnson in 1922 in the Journal of the 
Optical Society of America to describe "A 
Low Voltage Cathode-Ray Oscillograph," 
the first known practical instrument of this 
kind. A great many early references to 
the oscillograph are given in The Cathode- 
Ray Oscillograph in Radio Research, published 
by His Majesty's Stationery Office in Lon- 
don in 1933, and there is no reference to the 
word oscilloscope. This latter term has 
been widely used in the radio service field, 
but has not found great favor among 
engineers who are daily engaged in the 
study or design and development of 
cathode-ray oscillographs. This misuse of 
a word does not detract from the excellence 
of the material covered. 

In summarizing, the reviewer has found 
this book to be an exceptionally fine refer- 
ence work on the subject of cathode-ray 
oscillographs and their uses, and does not 
hesitate to recommend it as a valuable 
addition to engineering libraries every- 
where. Scott Helt, Research Div., Allen B. 
Du Mont Laboratories, Inc., 2 Main Ave., 
Passaic, NJ. 



Progress in Photography 1940-1950 

Editor-in-Chief, D. A. Spencer. Editorial 
Board, W. F. Berg, J. Eggert, L. E. Varden 
and T. A. Vassy. Published (1951) by 
The Focal Press, Ltd. Distributed by L. 
E. Varden, Pavelle Color, Inc., 533 W. 57 
St., New York 19. 450 pp. + 10 pp. 
appendix. 150 illus. 7 X 9 in. Price 
110.00. 

In 81 reports, 68 authors have recorded 
the progress of a decade in this volume. 
Some of their names are quite familiar to 
Journal readers. The opening article is by 
Glenn Matthews; E. W. Kellogg reports 
on sound recording; John Crabtree on 
processing; John Bradley on film storage. 

The broad base of photography is cov- 
ered by this book, with little detail given on 
any single phase; however, liberal refer- 
ence lists are appended to each chapter. 

Equipment progress is reported in terms 
of amateur equipment. There are some 
references to professional equipment. The 
new high-acetyl cellulose acetate film base 
gets one short chapter. Articles or chap- 
ters which include primarily motion picture 
subjects are: High-Speed Photography; 
Sound Recording for Motion Pictures; 
Recording with Galvanometer Oscillo- 
graphs; Cine Radiography; Visual Aids 
for Instruction; Time and Motion Study; 
Job Training; Propaganda, Selling Aids 
and Demonstration Films; and a descrip- 
tion of the functions and activities of the 
SMPTE. 

It should not be assumed, however, that 
these reports have interest for only the 
motion picture engineer. Considering the 
broad base of our membership we counted 
53 articles out of the 68 which have direct 
information bearing on some phases of our 
work. 

Perhaps it is too much to ask, with so 
many subjects crowded into less than 500 
pages, that a less selective annotation of 
equipment be employed! As we read 
some subjects we find, or sense, a partiality 
toward certain manufacturers. Important 
developments of competitors were not al- 
ways reported. The editor might have 
condensed the three references or descrip- 
tions of the Polaroid Land camera to a 
single entry and added a few other interest- 
ing developments in the inches he gained. 

The comment above, incidentally, ap- 
plies to non-U.S. contributors as well as to 



179 



our compatriots. (About a third of the 
authors are American.) 

Progress in Photography 1940-1950 should 
be a handy reference book with its inter- 
national basis, especially when supple- 
mented by the more detailed progress re- 
ports which appear in our Journal. It 
provides quick information on progress in 
England and Europe as well as our own, 
and the generous references will be of 
definite aid to the researcher. Its short- 
comings are outweighed by the more 
positive aspects of the book, and readers 
may well find it a useful tool. The illus- 
trative material is scanty but perhaps ade- 
quate. Don Bennett, Associate Editor, 
Photo Dealer Magazine, 251 Fourth Ave., 
New York 10. 



The Illumination of Photographic Dark- 
rooms and the Determination of the 
Spectral Sensitivity of Photographic 
Material 

By G. Weber. Translated from Danish 
into English by Vibeke Bonde. Published 
(1950) by the Academy of Technical Sci- 
ences and the Institution of Danish Civil 
Engineers on commission by G. E. C. Gad, 
32 Vimmelskaftet, Kobenhavn K., Den- 
mark. 280 pp. including appendix, bib- 
liography and 12 pp. index. 166 illus. 
6 X 9 in. Paper cover. Price Danish 
Kr. 16,50 (about $2.00). 

G. Weber, Professor of Illuminating 
Engineering at the Technical University of 
Denmark and President of the Danish 
Illuminating Engineering Society, has in- 
vestigated the theory applicable to a 
judgment of what is the maximum light 
tolerable to photographic materials and the 
minimum light needed for adequate 
working conditions. 

The author brings out the fact that dark- 
room illuminating should be chosen with 
regard to both the spectral sensitivity of 
the photographic materials to be handled 
and the sensitivity of the eye and that both 
of these sensitivities should be determined 
at the low intensities commonly used. In 
most cases this will require a source and 
filter combination. 

The author states "...that the filters 
should have maximum efficiency, i.e., their 
absorption must be such as to cause mini- 



mum reduction of the light in relation to 
the eye and maximum reduction in relation 
to the plate." Theoretical consideration 
and calculations are discussed at consider- 
able length and illustrative examples pre- 
sented in unusually great detail. Some, 
but much less, attention is paid to practical 
trial methods. Under the heading "Direct 
Determination of the Permissible Illumina- 
tion," there is recognition of the fact that 
in general the individual theoretical factors 
will not be precisely known. The state- 
ment, "None of these seven factors are 
known with any great certainty," is given 
as one reason for use of an experimental 
method. Again it is stated of the theo- 
retical method presented, "But even if all 
these quantities were known, the method is 
of course far too complicated for practical 
purposes, although it may be of a certain 
theoretical interest." 

This reviewer concurs in Dr. Weber's 
judgment; judged by this criterion, there 
are many, many pages "of a certain theo- 
retical interest" and relatively few pages 
devoted to procedures intended for "prac- 
tical purposes." D. R. White, Research 
Laboratory Director, Photo Products Dept., 
E. I. du Pont de Nemours & Co., Inc., 
Parlin, N.J. 



Audio Anthology 

Compiled from Audio Engineering, C. G. 
McProud, Editor. Published (1950) by 
Radio Magazines, 342 Madison Ave., 
New York 17. 124 pp. incl. 210 illus. 
8f X 9f in. Price $2.00. 

This compilation of 38 articles from 
Audio Engineering covers the period from 
May 1947 to December 1949. The selec- 
tion of material has been largely directed 
toward the audio hobbyist. Eleven of the 
articles are on audio amplifiers. The re- 
mainder are on the subjects of loudspeak- 
ers, dividing networks, equalizers, noise 
suppressors, volume expanders and radio 
receivers. 

Since the compilation is directed toward 
the audio hobbyist, the accent is on prac- 
tical construction rather than on theoretical 
design considerations. However, when 
design information is necessary for the pur- 
pose of the article, it is presented in an 
understandable and usable form, as for 



180 



example in the articles on loudspeaker 
enclosures, dividing networks and multiple- 
speaker matching. The amplifiers de- 
scribed cover the range from phonograph 
preamplifiers to 30- watt power amplifiers. 
A considerable amount of space (10 arti- 
cles) is devoted to the subject of frequency 
equalization, giving it a thorough coverage 
from a practical standpoint. G. W. Read, 
Westrex Corp., 6601 Romaine St., Holly- 
wood 38, Calif. 



Bibliography on Stereography 

Four hundred references have been pub- 
lished in mimeo form by the Stereo Society 
of America, covering magazines and jour- 
nals from this country and from abroad. 
The references have a wide range from 
editorials and popular articles to learned 
treatises. Copies of the Bibliography are 
available at $1.50 each from The Stereo 
Society of America, Inc., Owen K. Taylor, 
Secretary, 40 Monroe St., New York 2. 



New Products 



Further information about these items can be obtained from the addresses given. As in 
the case of technical papers, the Society is not responsible for manufacturers' statements, 
and publication of news items does not constitute an endorsement. 



Trade-marked the "Color-Tru Optical 
Bench," this equipment has been designed 
to enable the operator to judge intelligently 
the quality of photographic objectives and 
lens systems for most aberrations. Results 
are read directly by dial indicator in 
thousandths of an inch for comparisons 
between lenses. Attachments are avail- 
able for holding cameras in alignment, 
nodal slide, lens boards and lens barrels. 
Targets are those of the U.S. Bureau of 



Standards. Checks can be made of resolu- 
tion, color, focus, diaphragm location, 
effective aperture, cell separation, spherical 
aberration, element alignment and distor- 
tion. Prices range from $237.50 to 
$650.00, depending on accessories and on 
choice of microscope. The Color-Tru 
Optical Bench is available from Grover 
Photo Products, 2753 El Roble Dr., Los 
Angeles 41. 




181 




Curtis Color Analyst 




fit 



182 



fit 




Curtis Color Analyst for the large models. The intensity of any 

Color separation images may be evaluated, <* the three |uminants may be varied to 

and any necessary corrections determined, ad J ust the color balance of the image until 

with the Curtis Color Analyst, an inst^ * a PP ear / normal to the operator The 

ment developed and manufactured by extents of such variations are indicated by 

Curtis Laboratories, Inc., 2718 Griffith means of dials or meters calibrated m terms 

A i 0-7 n IT of exposure variations required to obtain 

Park Blvd Los Angeles 27, Calif. P reproduction from any 

The Color Analyst contains an optical ^ ^ J^. The light source y s 

system incorporating a beam splitter that ^ filters may be chosen tQ match most 

enables the operator to see a fused image in nearly the characteristics of thc inks, pig- 

color of three positive black-and-white sepa- ments Qr dyes of the final color reproduction 

ration images placed into the instrument, process. 

and illuminated by appropriately filtered A 20 X 24 in. model of the Color Analyst 

light. Positive transparencies are required has been built for the Milwaukee Journal 

for the 11 X 14 in. Color Analyst or smaller where it is used to check color separation 

models; black-and-white prints are needed prints and black-and-white ink proofs. 

Erratum 

"Progress Committee Report," Jour. SMPTE, vol. 56, p. 568, May 1951. 

Page 570, in title of Fig. 1 and in column 2, line 18: read Camerette for 
Cameflex. (This 16-/35-mm camera is known as the Cameflex in Europe 
but in the United States is the Gamerette, according to new information 
from the Benjamin Berg Agency, 1213 North Highland Ave., Hollywood 
38, Calif.) 

Meetings of Other Societies 

Biological Photographic Association, 21st Annual Meeting, Sept. 12-14, Kenmore Hotel, 

Boston, Mass. 
Theatre Equipment and Supply Manufacturers' Association (in conjunction with Theatre 

Equipment Dealers), Oct. 11-13, Ambassador Hotel, Los Angeles, Calif. 
National Electronics Conference, Seventh Annual Conference, Oct. 22-24, Edgewater 
Beach Hotel, Chicago. The conference is sponsored by the American Institute of 
Electrical Engineers, Institute of Radio Engineers, Illinois Institute of Technology, 
Northwestern University and the University of Illinois, with participation by the 
University of Wisconsin and the Society of Motion Picture and Television Engineers. 
The American Institute of Physics is holding a twentieth anniversary meeting in Chicago 
on October 23-27. Its member societies will hold meetings at that time as follows: 
Acoustical Society of America, Oct. 23-25 
Optical Society of America, Oct. 23-25 
Society of Rheology, Oct. 24-26 
American Physical Society, Oct. 25-27 
American Association of Physics Teachers, Oct. 25-27 

UFPA Fifth Annual Workshop 

On August 13-18 the University Film Producers Association held its fifth annual 
workshop on the campus of Indiana University. There was a formal program of 
panels on production problems such as scripting, sound techniques, films for television, 
distribution and animation as they affect the university film producer. Screenings of 
university productions were held at night. Housing was provided in one of the Uni- 
versity dormitories. Arrangements were under the direction of Harold Otwell, Audio 
Visual Center, Indiana University, Bloomington, Ind. 

183 






Method of 
driving wedft* 



A. Microammeter coil 

B. Telescope lenses 

C. Mirror 'spot' 
I). Range shift disc 

E. Colour matching dr 

K. Collecting lenses 

G. Optical edges 

H. Photo-electric eell 

1. Diffusing screen 

J. Dry battery 

K. Exposure, density ou.l 

brightness scales 
L. Stop and him speed sc 
M. Lamp switch 
N. Rheostat 



The Visual Photometer is a pocket-size 
visual-comparison photometer, with a 
brightness range of 1,000,000 to 1 and 
its own internal comparison source, 
made in England by Salford Electrical 
Instruments, Ltd. Zoomar Corp., 381 
Fourth Ave., New York 16, is the dis- 
tributor in the United States. The motion 
picture industry finds application for the 
SEI instrument in the production studio or 
on location for determining correct ex- 
posure and screen brightness in projection. 
A photocell and microammeter together 
with a potentiometer in the comparison 
lamp circuit provide a reference brightness 
adjustment independent of the brightness 
or color sensitivity of the observer's eye. 
Aging of the dry cell is thus compensated 
for. 

A pair of neutral density wedges gives 
the instrument a basic brightness range of 
100 to 1 and additional filters shift the 
range up or down by factors of 100 giving 
extended foot-Lambert range of from 0.01 



to 10,000. Two filters, one blue and one 
yellow, change the apparent color of the 
comparison spot to match the incident light 
color when reading brightness of an object 
illuminated in the first case by the sun, 
high-intensity carbon arc or "daylight" 
lamps, or in the second case by tungsten 
lamps or the "low-intensity" type of arc 
lamp. 

In use the comparison spot appears 
superimposed upon the object whose 
brightness is being measured. The wedges 
are then moved slowly until the spot blends 
into the background. By appropriate 
choice of scales it is then possible to deter- 
mine either brightness of the object in foot- 
Lamberts, or photographic exposure re- 
quired. Since the spot subtends ar angle 
of one-half degree, readings of small areas 
at inaccessible places such as drive-in 
theater screens, walls, ceilings and drapes 
that surround the screen in a motion pic- 
ture theater and high parts of studio sets 
are "naturals" for the SEI instrument. 



Back Issues of the Journal Available 

Three and one-half years of the Journal, July 1947 through December 1950, are avail- 
able at the job lot price of $25.00 from Mr. Max Prilik, c/o Circle Theater, 82 H Grant 
Circle, The Bronx 60, N.Y. 



184 



Foreword 

Symposium on Screen 
Viewing Factors 

By W. W. LOZIER, Chairman, Screen Brightness Committee 



THE SUBJECTIVE IMPRESSIONS received 
during the viewing of motion pictures 
are influenced by a great many factors. 
What the eye sees on the screen is the 
result not only of the conditions of the 
original scene, but also of the many steps 
of film processing and all the elements 
involved in the projection of the finished 
motion picture. 

The Screen Brightness Committee has 
long been interested in the problem of 
establishing a scientific basis for deter- 
mining preferred viewing conditions. 
The Committee sponsored a symposium 
on subjects pertaining to screen bright- 
ness at the Fall 1935 Convention of the 
Society. The record of this meeting, 
published in the May 1936 JOURNAL, 
summarized the state of knowledge at 
that time and served as the basis of 
formulation of a recommendation for 
projection screen brightness for 3 5 -mm 
motion pictures. Technological de- 
velopments since that time have greatly 
changed some of the basic factors in- 
volved. A summary of work done and 
current thinking on the problem of 
screen brightness was contained in a dis- 
cussion prepared by F. J. Kolb, Jr., and 
published in the April 1951 JOURNAL. 
Subsequently, the Screen Brightness 
Committee sponsored the Screen View- 
ing Factors Symposium at the May 2nd 



session of the Spring Convention of the 
Society in New York this year. It is the 
conviction of the Screen Brightness 
Committee that the definition of the pre- 
ferred conditions of viewing motion pic- 
tures is, in large measure, subject to 
scientific determination. The papers 
presented at the above-mentioned Sym- 
posium and published in the following 
pages are serious efforts and the first 
results of renewed activity in this direc- 
tion. 

E. M. Lowry, in his discussion of the 
luminance discrimination of the human 
eye, gives results of evaluation of the 
sensitivity of the eye, in this regard, as 
affected by the size and brightness level 
of the surrounding areas. MacAdam 
shows that the subjective impressions of 
hue and saturation are greatly influenced 
by the color quality of the surrounding 
light to which the eye is adapted. Criti- 
cal levels of illumination, below which 
marked impairment of visual perform- 
ance occurs, are indicated by Spragg in a 
study in a seemingly unrelated field 
which may, however, prove meaningful 
for motion picture viewing. Laboratory 
audience-preference studies by Guth 
relate preferred brightness levels of sur- 
rounding areas to the picture brightness. 
Logan, and Schlanger and Hoffberg 
present practical approaches to the prob- 



September 1951 Journal of the SMPTE Vol. 57 



185 



lem of illumination of the areas sur- 
rounding the screen in a motion picture 
theater. 

The "Report on Screen Brightness 
Committee Theater Survey" summarizes 
the results of measurement of screen 
brightness and related factors in 125 
representative motion picture theaters in 
this country and in 1 8 West Coast review 
rooms used for viewing 3 5 -mm motion 
pictures. The screen brightness for 
the majority of theaters is shown to be 
within or near the currently recom- 



mended standards, but there is a wide 
range of extreme values of brightness 
and other factors in a minority of the 
theaters which fall far outside the range 
of good projection practice. 

It is the sincere hope of the Screen 
Brightness Committee that the papers 
reported in these pages will serve to 
stimulate many other worth-while tech- 
nical studies on these subjects which will 
further assist in putting motion picture 
viewing on a scientific basis. 



186 



September 1951 Journal of the SMPTE Vol. 57 



The Luminance Discrimination 
of the Human Eye 



By E. M. LOWRY 



Data are presented to show not only the effect of the luminance to which the 
eye is adapted on its ability to discriminate differences in luminance, but also 
the effect of the visual angle upon this important ocular function. That 
luminance discrimination depends upon whether the observer's attention is 
fixed upon a highlight or shadow region is shown by data on threshold lumi- 
nance when scenes are being viewed in which the luminance varies over a 
wide range. 



_L HAT THE VISUAL comfort of the audi- 
ence in a motion picture theater has been 
of great interest for a long time is evi- 
denced by the many papers on the sub- 
ject of the projection screen and its sur- 
roundings, as well as by the activities of 
the Screen Brightness Committee of this 
Society. This interest arises in large 
part from the known fact that fatigue re- 
sults when the eyes are used over ex- 
tended periods in attempting to discern 
fine detail or to discriminate luminance 
differences when the luminance is so low 
that the visual system is working near its 
limit. As indicated by the title, this 
paper is concerned with the ability of 
the eye to discriminate differences in 
luminance. Its further purpose is to 
emphasize that, contrary to the often- 



Communication No. 1412 from the Kodak 
Research Laboratories, a paper presented 
on May 2, 1951, at the Society's Conven- 
tion, Screen Viewing Factors Symposium, 
at New York, by E. M. Lowry, Eastman 
Kodak Co., Kodak Park Works, Rochester 
4. N.Y. 



accepted notion, the sensitivity of the 
human eye to luminance differences is 
much more affected by the luminance of 
the region immediately surrounding the 
point of attention than by the average 
luminance of the scene. 

In the interest of clear understanding, 
some definition of terms is desirable. 
Throughout this paper, the word lumi- 
nance is used in place of brightness. l The 
unit of luminance is the foot-Lambert 2 
and is equal to the average luminance 
of a perfectly diffusing surface emitting 
or reflecting one lumen per square foot. 
That is to say, the average luminance 
in foot-Lamberts of any reflecting surface 
is the product of the illuminance in foot- 
candles by the reflectance of the surface. 

Luminance discrimination or contrast 
sensitivity has been the subject of much 
investigation since the classical work of 
KG nig and Brodhun some seventy years 
ago. A very large portion of the data 
collected has been under highly special- 
ized conditions, such as a restricted field 
of view, low luminance surround, an 



September 1951 Journal of the SMPTE Vol.57 



187 



f 02 



Ll 
= W 





Fig. 1. Plan view of Visual Sensitometer. 

artificial pupil, monocular viewing, etc. 
Such conditions have little, if any, re- 
semblance to those which exist when an 
observer is viewing a scene; for example, 
a landscape out of doors. Normally he 
observes with both eyes, and the lumi- 
nance may vary from nearly zero to 
thousands of foot-Lamberts. In addi- 
tion, almost every scene presents to the 
eye a variegated pattern of color. Not 
only changes of light and shade exist, but 
also a gamut of many hues of varying 
saturation, as well as objects of manifold 
shapes and sizes. As an end result, the 
entire visual field is a complicated design 
made up of a host of variables, each of 
which may in some way affect the per- 
ceptions of the observer. 

In an attempt to obtain numerical 
data under conditions simulating those of 
normal viewing, and yet provide ade- 
quate control of the factors of size of the 
visual field as well as of the test-spot 
luminance, and the luminance distribu- 
tion in the surround, an instrument, 



which we have called a Visual Sensitom- 
eter, was constructed. 

A plan view of this equipment is 
shown in Fig. 1. Here, H is a hemi- 
sphere one meter in diameter, with a 
conical-shaped cover, C. Both hemi- 
sphere and cover are painted inside with 
a matte white paint. At A is a test-field 
aperture of variable size and in the cover 
at E, a viewing aperture of sufficient 
diameter to permit placing the head of 
the subject in such a position that his 
visual field is almost 180. The position 
of the observer's eyes with respect to the 
test aperture is fixed by means of a head 
and chin rest. Illumination of the 
sphere is accomplished by means of a 
ring of lamps, d, and the luminance of 
the sphere wall, that is, the surround or 
adapting field, is controlled by a ring- 
shaped shutter, S, which is adjustable 
over the gap between the rim of the 
sphere and the cover. With this 
arrangement, the luminance of the sur- 
round can be adjusted from zero to 
approximately 1000 ft-L. 

Light from a biplane filament projec- 
tion lamp, O 2 , passes through the 
flashed opal glass, G, the lens, L b the 
neutral wedges, W, the lens, L 2 , the bi- 
prism, B, the totally reflecting prism, P, 
the lens, L 3 , the neutral filter, F, and the 
diaphragm, A, to the eyes of the observer 
at E. By means of this optical system, 
each eye of the observer views an aerial 
image of the biprism, B, in the form of a 
two-part field subtending an angle of 
1 .5 at the eye. The form of the field is 
shown in the insert at a. The luminance 
of the halves of this field is regulated by 
the neutral wedges at W, one of which 
can be adjusted by the person making 
observations. 

In making a series of settings either for 
luminance match or for just-noticeable 
difference in luminance, the subject 
turns a knob which moves one of the 
wedges until he is satisfied that one field 
either matches or is just higher or lower 
in brightness than the other. An assist- 
ant records the wedge setting. While 



188 



September 1951 Journal of the SMPTE Vol. 57 



CD 

< T 



1000 




100 



432101234 

Log Btf (ft. L.) 

Fig. 2. Luminance discrimination, AB tf , of the eye as a function of the 

test-field luminance, B,,, in foot-Lamberts for surround luminances of 

0, 1, 10, 100 and 1000 ft-L. 



the method of just-noticeable difference 
was followed in the work reported in 
earlier papers, 3 - 4 a slight modification of 
that technique was adopted when secur- 
ing the data presented here. Instead of 
setting for a just-perceptible difference 
between the two halves of the test field, 
the observer adjusted for equality of 
brightness and approached the balance 
point from each side. Five settings were 
made for each direction of approach to 
the balance point, and the average 
deviation from the mean was taken as a 
measure of the differential threshold, 
AB t f. The symbol AB t f is used to 
represent the difference in luminance be- 
tween the two halves of the test field, 
which is just at the border line of dis- 
cernibility. This method of securing the 
data seems to give the subject a little 
more confidence in reporting than when 
setting for least-perceptible difference, 
because it provides a somewhat more 
definite end point for his observations. 



In Fig. 2 are shown the data obtained 
for a series of luminances of the condi- 
tioning field, and each point plotted 
represents the average of from three to 
five runs on different days for each sur- 
round luminance. Probably the most 
noticeable feature of these curves is that 
above a certain luminance of the test 
field the discrimination remains con- 
stant, regardless of the surround, and 
that the slope of the curve is very nearly 
45. This, of course, means that the 
much-discussed Fechner Fraction is also 
constant above this value. There is 
absolutely no indication from the data 
that the ability of the human eye to dis- 
criminate difference in luminance de- 
creases even for values of the test field as 
high as 8000 ft-L. These results are in 
substantial agreement with those previ- 
ously reported by the author 3 and by 
Jones. 4 Data by Steinhardt, 5 and by 
Craik 6 also demonstrate that contrast 
sensitivity remains constant even at the 



E. M. Lowry: Luminance Discrimination 



189 



14 



12 



10 



o> 
S 8 

Q. 



100 



1000 




432101234 

Log Btf (ft. L.) 

A TJ 

Fig. 3. Ratio of -, plotted as a function of log B tf in foot-Lamberts for surround 

B tf 

luminances of 0, 1, 10, 100 and 1000 ft-L. 



highest values studied, which were 
approximately 10,000 and 4000 ft-L, 
respectively. 

By means of a special optical system, 
an attempt was made to determine 
whether a sufficiently high luminance of 
the test field would reduce visual sensi- 
tivity for luminance differences. With 
this setup, a two-degree test field yielded 
a maximum luminance of approximately 
32,000 ft-L, and, although rather per- 
sistent afterimages resulted, none of the 
observers participating in the test showed 
a decrease in his ability to detect a 
luminance difference of about 4%. In 
fact, each one reported that at the high- 
est luminance the contrast was at least as 
apparent, if not more so, than at the 
lower ones. Although this test was 
more qualitative than quantitative, it 



seems safe to state that at luminances 
considerably above those encountered in 
any practical situation the visual mecha- 
nism retains its ability to distinguish a 
constant fractional difference in lumi- 
nance. 

The data shown in Fig. 2 have been 
replotted in Fig. 3 as the more familiar 
AB/B as a function of log B t f. From the 
curves of this figure it will be seen that in 
the region of maximum luminance dis- 
crimination, represented by the flat 
portion of the curves, the ratio AB/B is 
just slightly over 1% and that this holds 
for test-field luminance above 0.3 ft-L 
for a dark surround. For higher values 
of surround luminance, namely, 1, 10, 
100 and 1000 ft-L, the straight-line por- 
tion of the curves begins at correspond- 
ingly higher luminances of the test field. 



190 



September 1951 Journal of the SMPTE Vol. 57 



1012 
Log surround luminance (ft. L.) 






Fig. 4. Luminance of subjective black for surround luminances of 0, 1, 10, 100 

and 1000 foot-L. 



Subjective Black 

Another aspect of the luminance dis- 
crimination of the eye which is of con- 
siderable importance is the luminance 
which will appear black. With the 
same equipment used in collecting data 
on contrast sensitivity, the visual thresh- 
old for luminance was determined with 
the same surround conditions as before, 
and the results are plotted in Fig. 4. As 
was the case with the differential thresh- 
old, so, with subjective black, the curve 
becomes linear above a surround lumi- 
nance of approximately 1 ft-L, and has a 
slope of about 45 degrees. This means 
that for a surround higher than 1 ft-L, 
the luminance which will appear black is 
a constant fraction of that to which the 
eyes are adapted. As the conditioning 
luminance is reduced to zero, the values 
for subjective black approach the thresh- 
old for the dark-adapted eye, and the 
curve becomes asymptotic to the axis of 
abscissas. 



Effect of the Size of the Surround 
on Threshold Luminance 

While it is necessary to have informa- 
tion as to how the visual system responds 
to luminance and luminance differences, 
it is also important to know the effect of 
the size of the conditioning field on this 
function. For this purpose, a simple in- 
strument called an "adaptometer" was 
built. It consisted of a brass tube 16 in. 
long and 1.5 in. in diameter, blackened 
both inside and out. In one end of the 
tube a small tungsten filament lamp was 
mounted behind a disk of flashed opal 
glass. In front of the opal glass was a 
black diaphragm with a 1-in. aperture 
which served both to limit the size of the 
field and to eliminate specular reflectance 
from the interior walls of the tube. By 
means of a long flexible wire cable, the 
lamp was connected to a 6-v storage 
battery through an ammeter, a rheostat, 
and a microswitch in the hands of the 
operator. The luminance of the opal 



E. M. Lowry: Luminance Discrimination 



191 



3.0 



2.0 



1.0 



0.0 




I I I I I I I I I 



8 



10 



12 



Visual angle in degrees 

Fig. 5. Luminance of subjective black as a function of visual angle for constant sur- 
round luminance, white target = 348 ft-L, gray rings 5.5 ft-L; x white target 
= 211 ft-L, gray rings 3.2 ft-L. 



glass in foot-Lamberts was measured for 
a series of filament currents, and a 
calibration curve of luminance as a 
function of current plotted. 

For the purpose of making readings, 
the observer took up his station at a dis- 
tance of 20 ft from the adaptometer. 
The instrument had previously been 
placed in line with the part of the scene 
to be investigated. Then, while viewing 
the opal glass, which at this distance sub- 
tended an angle of 15 min, through the 
open end of the blackened tube and 
against the background chosen, the 
observer adjusted the lamp current until 
by repeated interruptions of the current 
he could no longer distinguish a flashing 



of the light from the lamp. The lumi- 
nance of the opal glass at the current for 
disappearance of the flashing light repre- 
sented threshold luminance or subjective 
black. Of course, variation of the lamp 
current produced a change in the color of 
the light emitted, but, since the lumi- 
nances were quite low, it was felt that 
this effect could be neglected. Further- 
more, because of the small filament di- 
mensions, there was little lag between 
current pulses and filament temperature 
on either making or breaking the circuit. 
With this equipment set up behind a 
circular white target having a hole in the 
center to accommodate the end of the 
adaptometer tube, a series of threshold 



192 



September 1951 Journal of the SMPTE Vol.57 



determinations was made. The lumi- 
nance of the target was maintained at a 
constant value, and a number of differ- 
ent-sized black rings were placed on the 
white background to present a variety of 
sizes of visual angle. The size of the 
white target was 12 at the eye, and the 
rings varied in size from 0.5 to 12. 

Measurements at two luminance levels 
(Fig. 5), namely, 348 ft-L and 211 ft-L, 
demonstrated that for visual angles over 
about 3 the effect on subjective black is 
negligible. In other words, it is the 
luminance of the object which lies close 
to the point of fixation that primarily 
controls visual sensitivity. This same 
effect has been reported by Wright 7 and 
by Crawford. 8 In studies of motion 
picture projection, Reeb 9 found that only 
the luminance of the center of the screen 
was of importance and that varying- 
sized areas of the picture had no effect on 
the ability of the eye to distinguish 
differences in screen luminance. 

Threshold Luminance Under Field 
Conditions 

So far, the results reported have been 
those obtained in the laboratory under 
controlled conditions. In order to test 
the visual response when viewing outdoor 
scenes, the adaptometer, mounted on a 
tripod, was carried to the location 
selected and set up so that it was viewed 
with the various points of interest in the 
scene as the immediate surround. For 
purposes of record and future experi- 
ments, a camera was placed at the 
observer's station and the scene photo- 
graphed. Figures 6, 7 and 8 illustrate 
the instrument as used. The data 
printed on the figures show the lumi- 
nance at the point indicated as well as 
the value obtained for subjective black. 
Up to the present, only a few scenes have 
been investigated, so that the data can 
be nothing more than indicative. They 
have been plotted in Fig. 9, together 
with the curve for the threshold taken 
from Fig. 4. 

While at first sight there appears to be 



little correlation, and perhaps even some 
contradiction, between the values ob- 
tained in the laboratory and those re- 
sulting from observations in the field, a 
number of factors must be considered in 
drawing conclusions. It may be said, 
however, that the results do line up more 
or less in the order expected, that is, the 
lower the luminance of the area immedi- 
ately surrounding the adaptometer, the 
lower will be the luminance of subjective 
black. 

Visual phenomena as examined and 
reported by a large number of investi- 
gators have shown that what an observer 
perceives at any particular place in the 
visual field at a given time is dependent 
not only on the immediate stimulation, 
but also upon the preceding stimulation 
from the entire field and upon that from 
the region closely surrounding the test 
area. A part of the discrepancy, in the 
results reported here, is probably caused 
by the radical difference in the sur- 
rounds. In the laboratory, the adapting 
fields were uniform, while in actual 
scenes they were extremely nonuniform. 
Because of this lack of uniformity, the 
difference in completeness of adaptation 
for the particular area tested may well 
have been a contributing factor in the 
lack of agreement shown. It is very 
difficult to gaze steadily at a given point 
for two or three minutes until the eyes 
become thoroughly adapted to the 
luminance closely adjacent to the test 
field, and this is especially true when the 
surround consists of a complex pattern, 
such as is the case in the average outdoor 
scene. For the case of a uniform condi- 
tioning field, slight eye movements are 
not of great consequence, since the 
conditioning luminance remains con- 
stant. When a variable luminance is 
present, however, any slight shift in 
direction of view will result in a change of 
adaptation. 

In the opinion of the writer, the chief 
value to be derived from the data taken 
in the field is their evidence as regards 
the difficulty of interpreting the results of 



E. M. Lowry: Luminance Discrimination 



193 




Fig. 6. Illustration of the use of the adaptometer for field work. 




Fig. 7. Illustration of the use of the adaptometer for field work. 
194 September 1951 Journal of the SMPTE Vol.57 




Fig. 8. Illustration of the use of the adaptometer for field work. 



.5 

j 
O 
_O 

z 

2 T 



432101234 

Log surround in ft. L. 

Fig. 9. Results obtained for subjective black when viewing outdoor scenes. Solid 
curve represents data taken in the laboratory. 

x from Fig. 6; El from Fig. 7; O from Fig. 8. 



. M. Lowry: Luminance Discrimination 



195 



controlled experiments on visual func- 
tion in terms of practical problems. 
Before this may be done satisfactorily, a 
great deal more information must be 
obtained on the actual viewing situation. 

References 

1. L. A.Jones, " Color i me try: preliminary 
draft of a report on nomenclature and 
definitions," /. Optical Soc. Am., vol. 27, 
pp. 207-213, June 1937. 

2. Illuminating Engineering Nomenclature and 
Photometric Standards, Sec. 05.070, Illumi- 
nating Engineering Society, New York, 
1942. 

3. E. M. Lowry, "Some experiments with 
binocular and monocular vision," J. 
Optical Soc. Am., vol. 18, pp. 29-40, 
Jan. 1929. 

4. L. A. Jones, "Recent developments in 
the theory and practice of tone repro- 
duction," Phot. J., Sec. B, vol. 89B, pp. 
126-151, Nov.-Dec. 1949. 

5. J. Steinhardt, "Intensity discrimination 
in the human eye," /. Gen. PhysioL, vol. 
20, pp. 185-209, Nov. 1936. 

6. K. J. W. Craik, "The effect of adapta- 
tion on differential brightness dis- 



crimination,"/. PhysioL London, vol. 92, 
pp. 406-421, May 1938. 

7. W. D. Wright, Researches on Normal and 
Defective Color Vision, C. V. Mosby, St. 
Louis, Mo., 1947, pp. 230-231. 

8. B. H. Crawford, "The effect of field size 
and pattern on the change of visual 
sensitivity with time," Proc. Roy. Soc. 
London, vol. 129B, pp. 94-106, June 
1940. 

9. O. Reeb, "A consideration of the screen 
brightness problem," Jour. SMPE, vol. 
32, pp. 485-494, May 1939. 

Discussion 

Anon: Approximately how many sub- 
jects have you tested in each viewing 
situation? 

E. M. Lowry: We've had, in all, five 
different subjects. 

Anon: Did you get the impression that 
the results would have been much the 
same if you had used a great many more 
subjects? 

Mr. Lowry: The curves might have 
been somewhat more smoothed out with 
a greater number of subjects, but I believe 
the results would have been substantially 
the same. 



196 



September 1951 Journal of the SMPTE Vol. 57 



Influence of Color of Surround on 
Hue and Saturation 



By DAVID L. MACADAM 



Loci of constant hue are shown for daylight, tungsten light, and green and 
blue surrounds. Loci of constant saturation are shown for daylight and tung- 
sten-light surrounds. The effects of field size and simultaneous contrast are 
also shown. 



JL HE APPEARANCE of a projected color 
picture depends on the state of adapta- 
tion of the audience. This is governed 
by the picture itself, by its predecessors 
within the past few minutes, and, to an 
important extent, by the color of the 
light in the field of view surrounding the 
screen. This last factor is the subject of 
this paper. 

The effects of adaptation to various 
surrounding colors are qualitatively well 
known. Usually the picture appears to 
be off balance, with a predominant hue 
approximately complementary to the 
color of the surroundings. For this 
reason, chromatic surroundings are 
frowned upon by some makers of color 
films. Furthermore, even a neutral 
surround, albeit rather low in intensity, 
stabilizes the adaptation of the audience 
and causes them to notice unintentional 
variations of balance in a film. In an 
almost completely darkened theater, the 



Communication No. 1419 from the Kodak 
Research Laboratories, a paper presented 
on May 2, 1951, at the Society's Conven- 
tion Screen Viewing Factors Symposium, 
at New York, by David L. MacAdam, 
Eastman Kodak Co., Kodak Park Works, 
Rochester 4, N.Y. 



projected picture governs the adaptation 
of the audience so as to compensate, more 
or less completely, for accidental vari- 
ations of balance. Any illumination of 
portions of the visual field near the 
screen provides a reference white, so that 
variations of balance become more 
noticeable. For this reason, some mak- 
ers of color films strongly recommend 
that the light in the surroundings be kept 
to the bare minimum required for safety. 
As other speakers in this symposium 
have indicated, considerably more than 
the statutory minimum is necessary for 
comfort and "good seeing." Therefore, 
it seems desirable to have some quanti- 
tative data concerning the effects of the 
color of the surround on the hues and 
saturations perceived in projected pic- 
tures. Such data may indicate the best 
colors for surrounding illumination, so as 
to obtain optimum safety, comfort and 
vision with minimum disturbance of the 
hues perceived in the picture. Adequate 
data may indicate some condition of 
balance which, paired with a particular 
quality of light in the surround, will 
cause the least perceptible effects for 
normally expected variations of balance 
and auditorium lighting. 



September 1951 Journal of the SMPTE Vol. 57 



197 



G B 




Fig. 1. Schematic diagram (horizontal cross section) of twin colorimeter, 
observing booth and observer's eyes. 



To obtain and show such data, it is 
necessary to employ a method of measur- 
ing colors which is independent of vari- 
ations of adaptation of the observer. 
With such a method, it is possible to de- 
termine the variations of measured colors 
which are required to produce equivalent 
effects under various conditions of 
adaptation. 

A method, of the kind required for 
measuring colors and for representing 
the effects in which we are interested, 
was recommended in 1931 by the Inter- 
national Commission on Illumination. 
It was adopted by the American Stand- 
ards Association as a War Emergency 
Standard in 1942, and within the last 
month has been reaffirmed as a regular 
American Standard. 1 The method has 
been described previously in this 
JOURNAL. 2 - 3 The chromaticity diagram, 
which is commonly used to represent the 
results of color measurements, is very 
useful for representing and interpreting 
the results of quantitative research on 
color vision. Any color is always repre- 
sented by a fixed point in the chroma- 
ticity diagram, regardless of the effects of 



adaptation in changing the perceptions 
arising from that color. This property 
of the chromaticity diagram implements 
the psychophysical definition of color 4 as 
"characteristics of light." These charac- 
teristics are independent of the state of 
adaptation of the observer. On the 
other hand, the chromatic attributes, hue 
and saturation, of the sensation resulting 
from any color, depend very much on the 
observer's state of adaptation. The co- 
ordinates of the point representing a 
color do not change, but hue and satura- 
tion do, when the color of the surround is 
changed. 

The experimental arrangement used 
to get the desired data is indicated in Fig. 
1. This is a horizontal cross section 
through a twin colorimeter, the observ- 
ing room, and the observer's eyes. 5 The 
amounts of light passed by the red, green 
and blue filters, R, G, B, are varied by 
rectangular diaphragms, moved in verti- 
cal slots by remote control. These 
beams are mixed in the interiors of two 
hollow white spheres. The blended 
light within the spheres is viewed through 
portions of two plastic Fresnel lenses. 



198 



September 1951 Journal of the SMPTE Vol.57 



They appear as two adjacent semicircles. 
They are surrounded by a fluorescent 
cloth which glows with light of whatever 
color is desired. The cloth is irradiated 
with ultraviolet energy, which excites 
the surround but does not contaminate 
the colors of the light in the central field. 

Figure 2 shows series of points in the 
chromaticity diagram. Each series rep- 
resents colors of various saturations, all 
of which appear to have the same hue 
when seen with a black surround. The 
point W represents the color which 
appears to be white when no other colors 
are visible. The innermost point on 
each curve represents the color which 
appears to be white when the adjacent 
semicircle has the color represented by 
the outermost point. The differences 
between W and the innermost points, 
therefore, represent the effects of simul- 
taneous contrast, and indicate possible 
effects of various colors in a picture on 
the appearance of neighboring colors in 
the picture. 

Figure 3 shows series of colors which 
appear to have constant hue when sur- 
rounded by light matching the chroma- 
ticity of a blackbody at 3200 K. These 
curves are entirely different from the pre- 
ceding ones. Their center of conver- 
gence represents a color that appears 
white when seen alone in such surround- 
ings. The innermost point on each 
curve represents the color that appears 
white in such a surround, when seen side 
by side with the saturated color repre- 
sented by the outermost point. Figure 4 
shows the constant-hue series and the 
effects of simultaneous contrast in a blue 
surround, the color of which is indicated 
by the cross. Figure 5 shows constant- 
hue curves and the effects of simultane- 
ous contrast when the general surround 
is green. 

The preceding results were obtained 
with a test field subtending 12. Figure 
6 shows results obtained with a test field 
subtending 2, with a surround only 
slightly greenish compared to daylight. 
In this case, hues particularly easy to 



remember were chosen. Thus, the yel- 
low was neither greenish nor reddish, 
and the purple was not predominantly 
bluish nor reddish. The innermost ex- 
tremity of each curve again represents 
the color which appeared white in one 
semicircle, when the saturated color 
represented by the outer extremity was 
in the adjacent semicircle. 

The oval curve represents a series of 
colors of various hues but equal satura- 
tion, as judged by comparing neighbor- 
ing hues in the 2 field. 6 These com- 
parisons were begun at yellow and 
progressed through orange, red, purple, 
blue and green, back to yellow. The 
sequence was then reversed, with results 
which verified quite closely the results of 
the first sequence. The circle near the 
center represents the color of the sur- 
round, which at all times appeared as an 
acceptable white. 

Figure 7 shows similar results for the 
same hues, and for constant saturation, 
with a surround nearly matching the 
color of a 3200 K blackbody light source. 
The results for the two different colors of 
surround are compared in Fig. 8. The 
saturations corresponding to the con- 
stant-saturation ovals were not neces- 
sarily equal in the two surrounds. 

Very few data of the kind shown here 
have been published. Bouma and 
KruithoF identified sets of colors which 
appeared to have the same hues in 
several surrounds. They did not deter- 
mine constant-hue loci, estimate the 
saturations of their colors, or evaluate the 
effects of simultaneous contrast. As a 
matter of fact, they assumed the con- 
stant-hue loci to be straight lines radiat- 
ing from the point representing the sur- 
round, and they drew far-reaching con- 
clusions from extrapolations based on 
that assumption. 

Newhall, Nickerson and Judd 8 pub- 
lished curves of constant hue and satura- 
tion derived from observations of Mun- 
sell paper samples in daylight. Helson 
and Grove 9 studied the changes of hue, 
lightness and saturation of surface colors 



D. L. MacAdam: Influence of Surround Color 



199 



o\ 




O^ rOOJ 

do od 



ij 
II 

a. - 









IJ! 






. 
- 




s* 
s1 



s -^ 

sis 
s is 3 



song 
Co* 

q ^^^ 
5 5 
5 C 

Hi! 



^2 s 
et Sis 



200 



September 1951 Journal of the SMPTE Vol. 57 







* g 

o <u 



9 | 
d to o 

11 



CVJ O 

d 



o M> 



IO CvJ O 

odd 




8 



X ~ 



CVJ g 

I 

d ^ 
& 



vp in ^ 

odd 

x 



D. L. M acAdam: Influence of Surround Color 



201 




Fig. 6. Loci of named hues and of con- 
stant saturation in a 2 field, surrounded 
by daylight (shown by circle). 




in passing from daylight to incandescent- 
tungsten-lamp light. The meaning of 
their results is obscured by the fact that 
the color stimuli, adaptations and per- 
ceptions were all permitted to change 
simultaneously. To determine unam- 
biguously the effects of adaptation on 
color sensation, it seems advisable either 



0.6 



Fig. 7. Loci of named hues and of con- 
stant saturation in a 2 field, surrounded 
by incandescent-tungsten-quality light 
(shown by circle). 

Fig. 8. Comparison of loci of same hues, 
and of constant but not necessarily equal 
saturations, in 2 field surrounded by 
daylight (broken-line curves) and tung- 
sten light (solid-line curves). 

to keep the stimuli unchanged and report 
the hue and saturation resulting for 
different adaptations, or to readjust the 
stimulus for each adaptation so as to keep 
the hue and saturation unchanged, as 
was done by Hunt, 10 and as was done for 
hue, although not for saturation, in the 
present investigation. 

Within the past year, Richter 11 has 
published curves purporting to represent 
various degrees of saturation. These 
were interpolated and extrapolated from 
the curve shown by the broken line in 
Fig. 9. The solid curve is that shown in 
Fig. 6, for adaptation to daylight. Un- 
fortunately, Richter did not control the 
adaptation of his observer, nor determine 
what stimulus appeared white under his 
conditions of observation. Since his 
judgments of equal saturation were made 
with a dark surround, it might be pre- 
sumed that white is represented by the 



202 



September 1951 Journal of the SMPTE Vol. 57 



0.2 0,3 0.4 0.5 0.6 0.7 




O.I 



0.0 



0.0 O.I 



Fig. 9. Comparison of Richter's locus of constant saturation in dark surround 
with locus of constant saturation in daylight surround (solid-line curve). 



point marked with a question mark. 
This guess is based on determinations of 
white in dark surrounds by Priest, 12 
Helson and Michels, 13 Hurvich and 
Jameson, 14 and MacAdam. 5 However, 
the effects of simultaneous contrast, indi- 
cated by Fig. 2, must have resulted in a 
different criterion of white and a different 
basis for saturation for each hue. The 
interpolation of curves for other degrees 
of saturation in Richter's method was 
based on the implicit assumptions that 
white paper would appear white when 
seen through the instrument used to de- 
termine the curve in Fig. 9, and that the 
effects of simultaneous contrast would 
not disturb the criterion for white. 
Since he did not use any surround to con- 
trol adaptation, these assumptions do not 
seem to be admissible. Therefore, the 
curves Richter interpolated and ex- 
trapolated are of doubtful significance. 



In conclusion, it can be stated that the 
color of the surround influences, to an 
important extent, the hues and satura- 
tions perceived in a picture. The re- 
sults shown in Figs. 2 to 8 are intended 
as a guide in estimating the kind and de- 
gree of effects to be expected with 
various surrounds. These results also 
indicate that engineers can no longer be 
content with looking at colors. The 
effects of adaptation are too great to be 
ignored, and are too complicated for 
guesswork, or for reasoning based on 
casual impressions. In order to deal 
effectively with color, it is necessary to 
measure color. 

References 

1. American Standards Association, 
"Method of spectral photometric meas- 
urement of color," Z58.7.1, and 
"Method of determination of color 
specifications," Z58.7.2, 1951. 



D. L. MacAdam: Influence of Surround Color 



203 



2. D. L. MacAdam, "The fundamentals 
of color measurement," Jour. SMPE, 
vol. 31, pp. 343-348, Oct. 1938. 

3. D. L. MacAdam, "Quality of color 
reproduction," Jour. SMPTE, vol. 56, 
pp. 487-512, May 1951. 

4. Committee on Colorimetry, "The 
psychophysics of color," /. Opt. Soc. 
Am., vol. 34, pp. 245-266, May 1944. 

5. D. L. MacAdam, "Loci of constant hue 
and brightness determined with various 
surrounding colors," /. Opt. Soc, Am., 
vol. 40, pp. 589-595, Sept. 1950.| 

6. D. L. MacAdam, "Influence of visual 
adaptation on loci of constant hue and 
saturation," J. Opt. Soc. Am., in press. 

7. P. J. Bouma and A. A. Kruithof, 
"Hue-estimation of surface colours as 
influenced by the colours of the sur- 
roundings," Physica, vol. 9, pp. 957- 
966, Dec. 1942; ibid., vol. 10, pp. 36- 
46, Jan.-Feb. 1943; "Chromatic 
adaptation of the eye," Philips Tech. 
Rev., vol. 9, no. 9, pp. 257-266, 
1947/1948. 

8. S. M. Newhall, D. Nickerson and D. B. 
Judd, "Final report of the Optical 
Society of American Subcommittee on 
the Spacing of Munsell Colors," /. 
Opt. Soc. Am., vol. 33, pp. 385-418, 
July 1943. 

9. H. Helson and J. Grove, "Changes in 
hue, lightness, and saturation of surface 
colors in passing from daylight tb in- 
candescent-lamp light," /. Opt. Soc. 
Am., vol. 37, pp. 387-395, May 1947. 

10. R. W. G. Hunt, "The effects of day- 
light and tungsten light adaptation on 
color perception," /. Opt. Soc. Am., 
vol. 40, pp. 362-371, June 1950. 

11. M. Richter, "Untersuchungen zur 
Aufstellung eines empfindungsgemass 
gleichobstandigen Farbsystems," Z. 
wiss. Phot., vol. 45, pp. 139-162, 1950. 

12. I. G. Priest, "The spectral distribution 
of energy required to evoke the gray 
sensation," Sci. Papers, Bur. Standards 
vol. 17, pp. 231-265, 1921. 

13. H. Helson and W. C. Michels, "Effect 
of chromatic adaptation on achroma- 
ticity," /. Opt. Soc. Am., vol. 38, pp. 
1025-1032, Dec. 1948. 

14. L. M. Hurvich and D. Jameson, "A 
psychophysical study of white," /. 
Opt. Soc. Am., vol. 41, pp. 521-536, 
Aug. 1951. 



Discussion 

W. W. Lazier: I would like to have 
you go through briefly again what you 
did in the manipulation of those two parts 
of the test field. I missed something 
important in there and perhaps someone 
else did, because it seemed to me that 
if you had control over both halves of 
the field, and you were trying to make 
some sort of a photometric balance, you 
would come to a condition where they'd 
both be just the same. Now what did 
I miss in there? 

D. L. MacAdam: The observer never 
was asked to match a color completely. 
He was, for instance, asked to establish a 
yellow, which in his opinion was neither 
reddish nor greenish, in the right half of 
the field. Then, during the rest of that 
particular experiment, he did not touch 
the controls of the right half of the field. 
He adjusted the controls of the left half 
of the field in such a manner that he main- 
tained the same brightness and the same 
hue, but decreased the saturation. He 
continued this by small steps of desatura- 
tion all the way to white. He made 20 
or 30 such steps. It is easiest and cus- 
tomary to progress from the saturated 
hue to white in regular sequence. Each 
time, he desaturated the yellow a little 
more and kept the brightness constant, 
but the thing to which we asked the ob- 
server to pay most attention was to keep 
the same hue, neither too orange nor too 
green. Therefore, each time we recorded 
a set of data the field was not matched 
completely, but was matched according 
to only two of the three attributes of color. 
It was matched in hue and matched in 
brightness, but not in saturation. 

We did similarly for the saturation loci. 
In that case we asked the observer to 
change the hue. There was another 
difference from the constant hue experi- 
ment. In that, we kept the right-hand 
side of the field at its maximum possible 
saturation throughout the whole series. 
But in the equal saturation experiment, 
the observer changed the hues of both 
halves of the field in turn. First, he 
adjusted to obtain a moderate saturation of 
yellow in the right-hand side of the field, 
then the observer adjusted the controls 
of the left side to obtain an orange equal 
to the yellow in saturation and brightness. 



204 



September 1951 Journal of the SMPTE Vol. 57 



But, of course, it was a different hue. 
Then he left that side of the field alone 
and returned to the right-hand side of 
the field which he adjusted to an even 
redder orange, equal to the other half of 
the field in two attributes, saturation and 
brightness. But the third attribute, hue, 
was different. 

Dr. Lazier' Thank you, that helps a lot. 

M. W. Baldwin, Jr.: I have two ques- 
tions. First, were your observers ex- 
perienced or naive? 

Dr. Mac Adam: They were experienced 
in the use of this apparatus. We're very 
naive in subjective judgement. If we 
say that two colors appear to be equally 
saturated, no training has contributed 
to that judgement. 

Mr. Baldwin: My second question is, 
how did you convey to them what you 
meant by the word hue? 

Dr. MacAdam: We did not attempt to 
teach the observer what hue means. 
The purpose of the experiment is to 
determine what the observer means by 
hue. As a matter of fact, we did not use 
the word hue when telling the observer 
what to do. We asked him to choose a 
yellow, for instance, that he felt sure he 
could remember, one in which neither 
red nor green was noticeable. 



Mr. Baldwin: Would you have been 
successful with this if you had called in 
a mail girl as an observer? 

Dr. MacAdam: If we had called in a 
mail boy, he might not have been suffi- 
ciently interested in color. I think a 
mail girl would have served very well. 

Anon: Are there data now available 
in respect to the direct viewing of trans- 
parencies? Could your data be applied 
to the direct viewing of color trans- 
parencies? 

Dr. MacAdam: My impression is that 
it could be applied in a general way, that 
is, one could estimate rather closely the 
extent of the effect, of which we have 
been aware for a long time, that a colored 
surround influences the apparent balance 
of a picture. I think we could now say 
how much the balance is influenced and 
how much one would have to adjust the 
balance in order to compensate for the 
effect of the surround. As for the mutual 
color adaptation effects of details within 
the picture itself, I don't believe we have 
enough data. 

Anon: Thank you. The reason for the 
question is that there is now a Sub- 
committee of ASA charged with the 
responsibility of developing, possibly, an 
American Standard for the direct viewing 
of transparencies. 



D. L. MacAdam: Influence of Surround Color 



205 



Visual Performance on Perceptual 
Tasks at Low Photopic Brightnesses" 



By S. D. S. SPRAGG 



Subjects, rigorously screened for visual abilities, were tested on a variety of 
visual perceptual tasks. A brightness range of 0.005 to 6.0 ft-L (at the sub- 
ject's eye) was used. For each task a critical brightness level (approximately 
0.02 to 0.05 ft-L) was found, below which visual performance was impaired 
(as measured by speed and accuracy scores), and above which increases 
in brightness produced little or no improvement in visual performance. 
Implications are discussed. 



-L HE EXPERIMENTS described are part 
of a research project concerned with 
human visual performance as it is re- 
lated to problems of airplane cockpit and 
instrument illumination. More speci- 
fically, study has been made of the mini- 
mum brightness levels needed for the 
effective performance of visual perceptual 
tasks. Toward this end, experiments 
have been carried out on the speed and 



Presented on May 2, 1951, at the Society's 
Convention Screen Viewing Factors Sym- 
posium, at New York, by S. D. S. Spragg, 
University of Rochester, Rochester 3, N.Y. 

*The research reported here has been 
carried out on a research contract between 
the University of Rochester and the Air 
Materiel Command, U.S. Air Forces. 
The experiments described have been re- 
ported in the following memorandum re- 
ports and technical reports issued by the 
Air Materiel Command: MCREXD-694- 
21 (October 1948); MCREXD-694-21A 
(Dec. 1948); TR 6013 (Nov. 1950); and 
TR 6040 (Nov. 1950). Research articles 
describing these studies will also be forth- 
coming in the Journal of Psychology. 



accuracy with which subjects can read 
photographic reproductions of instru- 
ment dials as a function of the intensity 
of illumination provided. Studies have 
also been made on the adequacy of visual 
performance on such perceptual tasks as: 
judgments of magnitude of a common 
illusion, thresholds for perception of 
motion, accuracy of binocular depth 
perception, and performance on visually 
presented arithmetic tasks, all as a func- 
tion of the amount of illumination pro- 
vided. 

Young adult male subjects, rigorously 
screened so that they constituted groups 
with excellent visual abilities, served as 
subjects. They were tested on dial- 
reading tasks and other visual perceptual 
tasks. A brightness range of 0.005 to 6.0 
ft-L was used. For each task there was 
found a critical brightness level at 
approximately 0.01 to 0.1 ft-L, depend- 
ing on the task. At brightnesses below 
this level visual performance was increas- 
ingly impaired; above this level in- 



206 



September 1951 Journal of the SMPTE Vol. 57 



creases in brightness produced little or 
no improvement in visual performance. 
These findings suggest that for the 
night-time operation of equipment, and 
also for the viewing of complex visual 
stimuli at low illumination levels, bright- 
ness values should not be allowed to fall 
below 0.05 to 0.1 ft-L; on the contrary, 
they should be kept safely above this 
critical level in order to insure adequate 
visual perception. 

Introduction 

Instrument dials must often be read 
rapidly and accurately under conditions 
in which it is desirable to provide no 
more than the minimum amount of 
illumination necessary for the efficient 
performance of the task. Such condi- 
tions are found, for example, in the air- 
plane cockpit during night flying. It has 
seemed desirable in the night operation of 
military aircraft and, perhaps to a some- 
what lesser extent, for commercial air- 
craft, to attain and preserve as much 
dark adaptation on the part of the pilot 
and copilot as is feasible. 

This demand has posed the persistent 
problem of the amount and nature of 
illumination which will best meet the 
requirements of the situation. Taken 
separately, the ideals are incompatible. 
On the one hand it would be desirable 
to flood the cockpit with a high level of 
white (incandescent) light. Studies 
of visual acuity, speed and ease of reading 
and performing other visual tasks, sub- 
jects' stated preferences, etc., have fre- 
quently concluded with recommenda- 
tions for ambient illumination from 15- 
20 ft-c to 1 00 ft-c or even more. 

On the other hand, it would be desir- 
able to have no light or practically no 
light in the cockpit, so that pilot and 
copilot can achieve and maintain maxi- 
mum dark adaptation and thus be better 
equipped to see and recognize other air- 
craft, mountains and other aspects of 
the terrain, etc. 

A practical solution to the problem 
will obviously be a compromise between 



these two conditions. It will involve a 
determination of the effectiveness of 
visual performance under a range of 
intensities and spectral distributions of 
illumination which will: (a) permit 
satisfactory performance of visual per- 
ceptual tasks inside the cockpit (reading 
dials, etc.); and (b) maintain a level of 
dark adaptation sufficient for the pilot 
and copilot to deal adequately with 
visual stimuli coming from outside the 
cockpit. 

As a beginning in a series of studies de- 
signed to contribute toward the solution 
of the problem, our project has under- 
taken certain experiments attempting to 
relate visual performance (as indicated 
by the speed and accuracy of reading 
dials) to the illumination provided. 

Although speed and accuracy of dial 
reading constitute primarily a complex 
perceptual task rather than a simple 
acuity function, available information on 
the relationship between acuity and 
illumination is relevant in that it may 
suggest the general nature of the function 
as well as set a lower limit to performance. 

The early study of Konig, as well as 
other more recent studies, indicated that 
acuity varies as the logarithm of illumina- 
tion intensity, with the implication that 
even at high illuminations an increase in 
illumination will produce some incre- 
ment of acuity. 

Other workers, however, have reported 
that visual acuity increases with illumina- 
tion increase only up to a relatively 
modest level (such as 10 or 20 ft-c) and 
that the increase in acuity is hardly 
noticeable beyond this range. 

A great many recent studies, both 
military and civilian, have concerned 
themselves with factors determining 
acuity and other characteristics of visual 
performance, as a function of illumina- 
tion level, in a variety of task situations. 
This literature has been surveyed, with 
differing emphases, by Fulton and his 
co-workers, 1 by Lawrence and Mac- 
millan, 2 by Smith and Kappauf, 4 and 
others. 



S. D. S. Spragg: Visual Performance 



207 




Fig. 1. A sample bank 
of dials, 2.8-in. diam, 100 
X 10 scale. 



There is still need, however, for a 
relating of specific visual perceptual per- 
formances, such as dial reading, to a 
systematically varied range of illumina- 
tion values. That is the aim of the 
present study. 

Procedures and Results 

Subjects were cone dark-adapted to 
the illumination level being used and 
were then required to read banks of 
photographically reproduced instrument 
dials as rapidly and as accurately as pos- 
sible. Figure 1 shows a typical bank of 
12 dials. It will be noted that the scale 
is in ten-unit steps; thus, subjects have 
to interpolate to read to the nearest unit. 
Dials were 2.8 in. in diameter. 

Two incandescent lights at about 2400 
K were used as sources. They were 
mounted in cans and the illumination 
was controlled by means of ground-glass 
filters and accurately drilled apertures in 
interchangeable brass plates placed in 
the optical axis. A viewing distance of 
28 in. was used. 

Twenty young adult males who passed 
a rigorous visual screening were used as 
subjects. Preliminary practice on the 
task was followed by formal trials. 

On the formal trials each subject read 
1 cards of dials at each of five brightness 



levels. Time was recorded by the experi- 
menter's starting the timer after the sub- 
ject read the first dial and stopping it 
after he read the eleventh dial. The 
first and last dial readings in each card 
were eliminated from both the time and 
error data because of their relative unre- 
liability. Thus, the data for each subject 
consist of 100 dials read at each of five 
brightness levels. 

The levels of illumination were chosen 
as a result of exploratory experimentation 
which indicated that a rather sharp 
change in the difficulty of the dial-read- 
ing task occurs at a brightness of about 
0.02 ft-L. For this experiment, there- 
fore, two values were chosen which would 
closely bracket the suggested transition 
level, another value at slightly above 
cone threshold for the cone dark-adapted 
eye, one at 6.0 ft-L, and one at an inter- 
mediate level. The values selected 
were: 0.005, 0.018, 0.022, 0.296, and 
6.0 ft-L. 

Brightness measurements were made 
with a Macbeth Illuminometer used in 
the subject's position, and directed 
against an 11 X 14 in. sheet of unexposed 
but fixed photographic paper from the 
same stock as that of the dial reproduc- 
tions. 

A counterbalanced sequence of bright- 



208 



September 1951 Journal of the SMPTE Vol.57 



Table I. Dial-Reading Performance as a Function of Task Brightness 
(2.8-in. Dials; N = 20 Subjects) 



No. (and %) 
of readings in 

Brightness, error in reading Standard 
ft-L 100 dials deviation 



Mean reading 
time per dial, Standard 
in seconds deviation 



0.005 


67.3 


10 


2.84 


.93 


0.018 


59.9 


14.1 


2.64 


.74 


0.022 


30.1 


8.1 


1.52 


.21 


0.296 


27.8 


5.5 


1.33 


.21 


6.0 


27.8 


4.4 


1.30 


.22 



ness levels was employed. Subjects com- 
pleted the experiment in two sessions, 
several days apart. They were given no 
knowledge of results; that is, they were 
not told the correct readings, nor whether 
their readings were correct or wrong. 

Table I summarizes the mean error 
frequencies and the mean total times. 
Each point is based upon 100 dials read 
by each of 20 subjects, therefore, upon 
2000 readings. 

Variances for subjects and for bright- 
ness levels were significant at the 1% 
level. An analysis by the "t test"* 
showed that, both for error frequency 
and for time, all differences that crossed 
0.02 ft-L were significant at the 1% level, 
while no difference that does not cross 
this brightness value is significant at the 
1% level. In fact, only one of them 
(error frequencies at 0.005 and 0.018 
ft-L) is significant at the 5% level. 

The error-frequency data are sum- 
marized graphically in Fig. 2 (results for 
2.8-in. dials), and the data for average 
reading time, in Fig. 3 (also 2.8-in. dials). 
Inspection of these two figures shows 



* The t test is a statistic frequently used to 
evaluate the probable genuineness of an 
obtained difference between two sets of 
means. For example, a difference which 
the t test shows to be "significant at the 
1% level" is a difference which would 
have occurred by chance fluctuation only 
1 time in 100, and therefore can be re- 
garded with a high degree of confidence 
as a genuine difference (cf. the sections 
on small sample statistics in a standard 
statistics textbook). 



that the error curve and the time curve 
are highly similar. By both measures, 
there is strong evidence that in this rather 
complex visual perceptual task there is 
marked improvement at about 0.02 ft-L 
and relatively little improvement there- 
after, at least up to 6.0 ft-L. We have 
made informal observations indicating no 
significant improvement at levels con- 
siderably higher than this. 

Because of the fact that these findings 
are based on fairly large dials with widely- 
spaced scale divisions, it was decided to 
repeat the experiment with smaller dials 
and finer scale-division spacings. Ac- 
cordingly, a second experiment was run, 
using dials which were 1.4 in. in diam- 
eter and had scale marks for every unit 
instead of every ten units, as in the above 
experiment. 

The general procedures were the same 
as in the preceding experiment. Ten 
subjects were used and (because of the 
setup demanded by another concurrent 
study) brightness levels of 0.005, 0.01, 
0.05, 0.1, and 1.0 ft-L were employed. 

The results of this experiment are 
summarized in Table II which shows the 
proportional error frequency and the 
mean time required, for the several 
brightness levels. It will be seen that 
there is a sharp improvement in perform- 
ance up to 0.1 ft-L and relatively slight 
improvement above that level. 

The results for the 1.4-in. dials are 
shown graphically in Figs. 2 and 3, in 
which are plotted the error data and the 
time data. Again it will be seen that 



S. D. S. Spragg: Visual Performance 



209 



100 



80 



60- 
<n 
o 



20 

8 

K 
U 

Q- 




Fig. 2. Frequency of 
errors in reading large dials 
(2.8-in. diam, 100 X 10 
scale) and small dials (1.4-in. 
diam., 100 X 1 scale) as a 
function of brightness. 



-3-2-1 I 

LOG I, IN FOOT - LAMBERTS 



Table II. Dial-Reading Performance as a Function of Task Brightness 
(1.4-in. Dials; N - 10 Subjects) 



No. of 






readings in 




% of readings 


error in 




in error in Mean reading 


Brightness, reading 50 
ft-L dials 


Standard 
deviation 


reading 50 time per dial, Standard 
dials in seconds deviation 


0.005 31.3 


8.0 


62.6 3.45 1.33 


0.01 20.8 


7.8 


41.6 2.79 0.66 


0.05 5.7 


4.0 


11.4 1.77 0.21 


0.1 3.9 


2.8 


7.8 1.71 0.24 


1.0 3.2 


2.1 


6.4 1.55 0.21 




M 













i 4.0 






o 
Jn ^ 






z 3.0- \ 






* \ 






2-0- \ 14 


" DIALS 


Fig. 3. Mean time in 


Lj^- 


__^ 


seconds required to read 


a! 6 




3 large dials (2.8-in. diam, 100 


% 1.0 

h- 


2.8 "DIALS 


X 10 scale) and small dials 
(1.4-in. diam, 100 X 1 


z 




scale) as a function of 






brightness. 



3-2-1 I 

LOG I , IN FOOT - LAMBERTS 



210 



September 1951 Journal of the SMPTE Vol.57 



performance improves markedly with 
increased brightness up to the 0.01-0.1 
brightness level, but there is little im- 
provement in performance above this 
level. 

Inspection of Figs. 2 and 3 permits a 
comparison of results for the larger, 
coarse-scaled dials and the smaller, fine- 
scaled dials. It will be seen that: (a) at 
the lowest brightness level, performance 
is about the same, approximately two- 
thirds of the readings being in error in 
each case; (b) between 0.01 and 0.1 ft-L 
there is rapid improvement in both cases, 
and relatively little improvement above 
this level; and (c) that performance 
levels off at a poorer performance value 
for the large dials, with their widely- 
spaced scale divisions and the necessity 
for making interpolations, than it does 
for the smaller, more finely-spaced dials 
where no interpolations are necessary. 

The same comparison can be made for 
time scores. Very little difference in 
results is to be noted here. If anything, 
performance is somewhat slower with 
the smaller, finely-spaced dials. 

These results seem to indicate that 
there is a critical brightness level below 
which subjects find it difficult to perform 
this dial-reading task, as shown by rela- 
tively slow responses and greater fre- 
quency of errors. Above this level, the 
task becomes suddenly much easier, re- 
sponses are quicker, and frequency and 
magnitude of errors much less. Further 
increases in brightness, however at 
least up to 6.0 ft-L and very probably 
indefinitely produce no further incre- 
ments of performance. It seems as 
though once a subject has been given just 
enough brightness to perform this task 
with ease, brightness is no longer a 
significant variable. 

This finding is in interesting contrast 
with Konig's classical curve relating 
acuity to brightness, and to the findings 
of certain recent investigators that acuity 
continues to increase even at very high 
brightness levels. Other workers, whose 
data indicate that acuity ceases to in- 



crease beyond a certain brightness level, 
have usually reported that their curves 
do not flatten out until about 5 to 10 ft-c 
of illumination. 

No real discrepancy exists between such 
findings and the present results. Our 
data were taken in a complex perceptual 
task in which adequacy of performance 
is a function not only of acuity and con- 
trast, but also of speed and accuracy in 
making the complex judgment which an 
interpolation represents. Since we are 
dealing with a task which is far more com- 
plex than a simple resolving power func- 
tion, the lack of close correspondence be- 
tween our results and the earlier acuity 
studies should not be disturbing. 

I wish to mention some further studies 
in this general area which were carried 
out by Dr. Milton L. Rock of our proj- 
ect. 3 The problem undertaken was a 
systematic examination of the adequacy 
of performance of four rather widely- 
varied visual perceptual tasks over a 
range of low photopic brightnesses. 
The tasks chosen were: (1) magnitude 
of judgment error in a conventional 
Miiller-Lyer illusion figure; (2) abso- 
lute threshold for perception of move- 
ment of an alternately black and white 
striped field; (3) accuracy of binocular 
depth perception in a modified Howard- 
Dolman type apparatus; and (4) per- 
formance in a series of visually presented 
addition tasks (a 3-digit number followed 
by a 2-digit sum, and the subject is re- 
quired to state whether it is or is not the 
correct sum of the first three digits). 
These four tasks were chosen to repre- 
sent a rather wide range of visual per- 
ceptual tasks as far as complexity is con- 
cerned. 

Subjects, screened visually as in our 
previous experiments, were tested on 
these tasks at the following brightness 
levels: 0.005 (which is just above cone 
threshold for the cone dark-adapted eye), 
0.01, 0.05, 0.10, and 1.0 ft-L. The view- 
ing distance was 28 in. for each task. 

I am not going to describe the details 
of these four experiments, but shall 



S. D. S. Spragg: Visual Performance 



211 



attempt to indicate briefly the principal 
results. 

For the Mtiller-Lyer figure, mean 
errors in judgment decreased sharply as 
brightness increased from 0.005 up to 
0.05 ft-L, but there was practically no 
improvement for brightnesses higher than 
this value. 

For the experiment on absolute motion 
threshold performance improved sharply 
as brightness was increased from the 
lowest values up to 0.1 ft-L, then only 
slightly from there up to 1.0 ft-L. 

For the depth perception experiment, 
increased brightness brought a marked 
increase in accuracy of judgments from 
the lowest brightness up to 0.05 ft-L and 
little or no increase above this level. 

Finally, in the addition task, improve- 
ment in performance was marked from 
the lowest level up to 0.05 ft-L, then 
stayed at essentially the same value for 
the two highest brightness levels. 

For all four of these visual tasks, when 
performance is plotted against bright- 
ness level we find rapid improvement in 
performance as brightness is increased 
up to a certain level and beyond this 
level, increases in brightness bring rela- 
tively slight increments of performance. 
This critical level seems to be between 
0.01 and 0.05 ft-L for the Muller-Lyer, 
the depth perception, and the addition 
tasks, and between 0.05 and 0.1 ft-L 
for the motion threshold task. It will 
be recalled that in the dial-reading ex- 
periments this critical value was esti- 
mated to be about 0.02 ft-L in one ex- 
periment and between 0.01 and 0.05 ft-L 
in the other. 

Conclusions 

Evidence seems to be accumulating 
that for visual tasks of a perceptual 
nature (in contrast to simple acuity func- 
tions) there is a critical brightness level 
(probably between 0.01 and 0.1 ft-L, 
depending on the task) below which sub- 
jects find it difficult to perform the task, 
and performance is relatively poor, 
while above this value the task becomes 



much easier, responses are faster and 
more accurate, and additional incre- 
ments of brightness make relatively little 
difference. 

From a practical standpoint, the find- 
ings from these studies indicate that in 
visual perceptual situations where maxi- 
mum performance is required with a 
minimum of brightness (in order, for 
example, to conserve dark adaptation), 
great care should be taken that the 
brightness level not be allowed to drop 
below about 0.05 to 0.1 ft-L. 

These findings have implications for 
the night operation of equipment, e.g., 
aircraft, and also for the viewing of 
complex visual stimuli at low levels of 
illumination. If the visual material to 
be perceived has a brightness safely 
above 0.05 ft-L, then the visual percep- 
tion of that material will be as rapid and 
as accurate as it would be if the bright- 
ness were at higher levels (at least up to 
6 ft-L, and possibly indefinitely). Our 
results do not, however, provide data 
bearing on the problems of: (1) fatigue 
effects of long-continued viewing under 
these conditions; or (2) individual 
preferences. Further research is needed 
to supply information here. 

References 

1. J. F. Fulton, P. M. Hoff and H. T. 
Perkins, A Bibliography of Visual Litera- 
ture, 7939-7944, Geo. Banta, Minasha, 
Wis., 1945. 

2. M. Lawrence and J. W. Macmillan, 
Annotated Bibliography on Human Factors 
in Engineering Design, Aviation Br., Re- 
search Div., BuMed, U. S. Navy, 1946. 

3. M. L. Rock, "Visual performance as a 
function of low photopic brightness 
levels," USAF, Air Materiel Com- 
mand, TR 6013, Nov. 1950. 

4. W. M. Smith and W. E. Kappauf, 
"Studies pertaining to the design and 
use of visual displays for aircraft instru- 
ments, computers, maps, charts, and 
tables," USAF, Air Materiel Command, 
TSEAA-694-1G, May 1947. 

5. S. D. S. Spragg and M. L. Rock, "Dial 
reading performance as related to 
illumination variables. I. Intensity," 



212 



September 1951 Journal of the SMPTE Vol. 57 



USAF, Air Materiel Command, MCR- 
EXD-694-21, Oct. 1948. 
6. S. D. S. Spragg and M. L. Rock, "Dial 
reading performance as related to 
illumination variables. III. Results 
with small dials," USAF, Air Materiel 
Command, TR 6040, Nov. 1950. 

Discussion 

Ben Schlanger: Was consideration given 
to the time factor, that is, do you know 
the effect after one or two hours of viewing? 

S. D. S. Spragg: Our experimental session 
typically lasted forty to forty-five minutes 
and there was no significant change in 
performance toward the end of this period. 
Our data, however, do not contribute 
anything to what might be called fatigue 
studies. Our results have no implications 
for continuous viewing that may extend 
for several hours under these conditions, 
although there are relevant studies which 
show that visual fatigue in tasks of this 
sort is almost impossible to demonstrate. 
Dr. Brian O'Brien has shown that, and 
Carmichael and Dearborn have also 
shown it for periods up to, maybe, seven 
or eight hours. 

O. W. Richards: Your work was done 
at relatively close distances. I was wonder- 
ing if you have any information that would 
apply to farther distances where con- 
vergence and other factors wouldn't enter. 
In other words, do you view this as entirely 
a general factor or do you think it involves 
other problems? 

Dr. Spragg: These experiments were all 
carried out at 28-in. distance which is the 
standard distance recommended for re- 
search on visual performance, or prob- 
lems, in the cockpit, as specified by the 



Visual Standards Committee of the NRC 
Vision Committee, and it is an extrapola- 
tion to generalize from our data to distant 
conditions. The details of our visual task 
were never much less than five minutes 
of angle and were all viewed at 28-in. 
distance. 

Anon: Dr. Spragg, can you tell me, 
regarding visual acuity and low brightness, 
what effects of color, primarily red, were 
shown in the study? 

Dr. Spragg: We have carried out two 
studies on dial reading under different 
qualities of illumination, using Corning 
sharp cut-off filters. I didn't report 
them here because I wanted to restrict 
this report primarily to the brightness 
problem. I might say, very briefly, that, 
as you suspect, we're interested in the 
red and yellow region because that region 
of the spectrum is important for main- 
tenance of dark adaptation. We found 
that if we took a good deal of care to 
make the color values equal, as deter- 
mined by heterochromatic color matching, 
so that we could say that we had red 
at 0.1 ft-L, red at 0.01 ft-L, and also 
yellow and other colors at the same value, 
that color made no difference if we stayed 
above this critical level of about 0.02 
ft-L; that is, performance was neither 
worse nor better with red, orange or 
yellow than it was with green. However, 
if we got below 0.02 ft-L, color still didn't 
seem to make very much difference, but 
red was worse than the other colors 
viewed. Thus, if red illumination is 
used for night operations and for reading 
instruments, it would seem more than 
ever crucial to keep the red illumination 
above this 0.02 ft-L level. 



S D. S. Spragg: Visual Performance 



213 



Surround Brightness: Key Factor 
in Viewing Projected Pictures 



By SYLVESTER K. GUTH 



The lighting of areas where projected pictures are viewed presents a number 
of specialized problems to the lighting engineer. However, these specialized 
problems involve factors of lighting design rather than any particularly un- 
usual visual factors. Basically, projected pictures are visual tasks upon which 
the eyes and attention of the viewers are concentrated for extended periods. 
Since the viewing of projected pictures is a seeing task, two distinct objectives 
are suggested: (1) providing maximal visibility of the task; and (2) providing 
maximal visual comfort and ease of seeing. These are fundamental objec- 
tives that must be satisfied in order to obtain optimal seeing conditions in any 
visual situation. This paper is confined chiefly to the second objective and to 
those factors which determine whether the area in which projected pictures 
are viewed is visually satisfactory. The screen is introduced only insofar as 
it influences or is influenced by the environmental factors. 



HE BRIGHTNESS characteristics of 
various portions of the visual field sur- 
rounding the central or task area are of 
overwhelming importance in providing a 
comfortable visual environment. 1 These 
brightnesses, and their relationships to 
the brightnesses of the task, contribute 
favorably or unfavorably to the seeing 
conditions. They may influence di- 
rectly the visibility of the visual task, or 
their effects may be more subtle and 
result in decreased ease of seeing. Obvi- 
ously, both effects may be and often are 



Presented on May 2, 1951, at the Society's 
Convention Screen Viewing Factors Sym- 
posium, at New York, by Sylvester K. 
Guth, General Electric Co., Nela Park, 
Cleveland 12, Ohio. 



produced simultaneously, especially 
when prolonged seeing is involved. 

The difficulty of obtaining adequate 
auditorium brightnesses in theaters has 
often resulted in minimizing the impor- 
tance of the surround brightnesses for 
ability to see and comfort of viewing. 
The lack of reports of discomfort has 
been used as one of the principal argu- 
ments for considering that there is 
nothing wrong with the existing viewing 
conditions. Such lack of complaints 
should merely be taken as the audience 
acceptance of what it is used to, just as it 
has done in many other fields. Since 
the motion picture is a visual task, the 
consideration of light and lighting can 
and should include the same factors that 
apply to other visual situations. 



214 



September 1951 Journal of the SMPTE Vol. 57 



ISO*, 



180" 




330' 



Fig. 1. A diagrammatic representation of the monocular and binocular visual fields. 

The portions occupied by a motion picture screen when viewed at three distances, corre- 
sponding to the screen width W, 3 W and 5 W, are illustrated by rectangles A, B and C, 
respectively. Shaded areas (right and left) represent portions of the visual field seen only 
by the right and left eyes, respectively. Unshaded area represents that portion of the 
visual field seen by both eyes. 



Basic Considerations 

In order to understand the importance 
of the surrounding conditions in the 
central field, it may be well to consider 
briefly the relative magnitudes of the 
two areas. The angular extent of the 
entire binocular visual field varies with 
the individual physiognomy and aver- 
ages about 200 horizontally and 130 
vertically, and is approximately elliptical 
in shape. The limits of various portions 
of the visual field are illustrated in Fig. 1 . 
The unshaded area indicates the portion 
of the visual field in which objects can be 
seen by both eyes. The two shaded 
areas on the right and left represent 
those portions of the visual field that can 
be seen only by the right and left eyes, 
respectively. 



The Task Area. A visual task usually 
occupies a limited region in the central 
portion of the visual field and its appar- 
ent or visual size is a function of the dis- 
tance from which it is viewed. A motion 
picture screen, for example, appears 
large or small depending upon whether 
it is viewed from the front or rear of a 
theater. The three rectangles super- 
imposed upon the visual field, illustrated 
in Fig. 1, represent a motion picture 
screen viewed from three different posi- 
tions in an auditorium. In order to be 
applied generally to any size screen, the 
viewing distance is expressed in terms of 
the screen width, W. Thus, a screen 
viewed at a distance corresponding to 
the screen width, W, is represented by 
rectangle A, the angular extent of which 



Sylvester K. Guth: Surround Brightness 



215 



Table I. The Visual Size and Area of a Screen When Viewed at Various Distances 



Viewing 
distance 
in screen 
widths 


Angular subtense 
of screen degrees 
Width Height 


Solid angle 
subtended 
by screen 
steradians 


Per cent of 
visual field 


W 
2W 
3W 
4W 
5W 
6W 
IW 
8W 


53.1 
28.1 
18.9 
14.3 
11.4 
9.5 
8.2 
7.2 


41.1 
21.2 
14.3 
10.7 
8.6 
7.2 
6.1 
5.4 


0.75 
0.19 
0.083 
047 
0.030 
0.021 
0.015 
0.012 


15.0 
3.8 
1.7 
0.94 
0.60 
0.42 
0.30 
0.24 



is about 53 horizontally and 41 
vertically. If the screen is viewed from 
the rear part of an auditorium, or a dis- 
tance of 5 W, it occupies a much smaller 
portion of the visual field and may be 
represented by rectangle C. When 
viewed at this distance, it extends 
approximately 11 horizontally and 8 
vertically. The intermediate rectangle 
B corresponds to a viewing distance of 
about 3 times the screen width. It 
should be noted that in some theaters a 
screen may appear even smaller than the 
one indicated by C. 

It is seen that even when the screen is 
viewed from a short distance, it occupies 
a relatively small portion of the binocular 
visual field. The importance of the 
peripheral regions can be emphasized by 
considering the relative areas involved. 
A convenient and expressive unit of 
apparent area is in terms of the solid 
angle, Q, in steradians,* subtended by a 
surface which combines the actual pro- 
jected area with the distance from the eye 
to the center of the surface. Thus, the 
relative extent of a surface can be ex- 
pressed as a percentage of the total solid 
angle subtended by the entire binocular 
visual field which is approximately 5 
steradians. The solid angle subtended 



* The solid angle, (, in steradians is equal 
to the projected area of a surface divided 
by the square of the distance from the sur- 
A 



face to the eye; i.e., Q, 



Z) 2 ' 



by a motion picture screen is dependent 
upon its actual size and the distance 
from which it is viewed, and both of these 
may vary over a considerable range. 
However, when the viewing distance is 
expressed in terms of the screen width, 
W, it is possible to illustrate the ranges of 
apparent sizes of screens as in Table I. 
It is seen that as the viewing distance in- 
creases, the angular extent of the screen 
diminishes rapidly between W and 2 W, 
and progressively more slowly for dis- 
tances greater than 2W. A more 
significant comparison is the solid angle 
in steradians subtended by the screen 
and the per cent of the visual field occu- 
pied at various viewing distances. Ex- 
cept for those who sit very close to the 
front of the theater, the screen occupies 
less than about 4% of the visual field, 
and for the average viewer less than 1%. 
Thus, it is obvious that the magnitude of 
the peripheral region of the visual field 
makes it extremely important to the 
viewer of projected pictures. Conse- 
quently, this area cannot be neglected 
when designing the lighting for comfort- 
able seeing conditions. 

When it is considered that the viewing 
of projected pictures involves a dynamic 
rather than a static visual situation, the 
area immediately surrounding the screen 
becomes even more important. In 
order to see all of the picture details, the 
eye may rove over the entire screen, the 
angular movement depending upon the 
viewing distance. Thus, at times, the 



216 



September 1951 Journal of the SMPTE Vol.57 



line of vision may be directed toward the 
edge of the screen and then the screen 
surround is close to the line of vision. 
For the longer viewing distances, a rela- 
tively small angular movement of the 
eyes will bring the screen surround into 
nearly direct view. Therefore, unless 
the surround brightness has been prop- 
erly adjusted, the viewer is faced with a 
considerable variation in adaptation 
brightness which can do nothing but de- 
tract from his pleasure and comfort by 
providing an undesirable visual environ- 
ment. 

When designing lighting, it is neces- 
sary to consider the various character- 
istics and requirements of the visual task. 
While the viewing of projected pictures 
usually involves prolonged periods, the 
task involves some factors that are differ- 
ent from those pertaining to other tasks 
such as reading. Much of the informa- 
tion or the story is obtained by words and 
the gestures, facial expressions and ac- 
tions of the performers. Therefore, 
visual acuity is less important than the 
discrimination of a wide range of bright- 
ness contrasts. The viewer is not con- 
fronted with the problem of resolving 
small details near the threshold in size. 
However, while discrimination of the 
characteristics of the visual task may not 
be critical, the eyes and attention are 
focused steadily with but brief respites. 

Adaptation Brightnesses. In any specific 
situation, the desirable surround bright- 
ness is dependent upon the brightness 
level to which the eyes are adapted. 
Therefore, it is necessary to determine 
the relationship between the picture 
brightness and the surround brightness. 
However, the former varies over a con- 
siderable range, depending upon projec- 
tion-equipment, theater and screen sizes, 
film characteristics, etc. It may range 
from a very low level for the opaque 
projectors used in educational work to 
the high levels obtained with slide pro- 
jectors. Nevertheless, it is possible to 
develop a concept in terms relative to 
the screen brightness obtained with the 



projector running without film. Fur- 
thermore, since a motion picture, or any 
sequence of projected still pictures, pre- 
sents a continuously variable brightness 
pattern, it is difficult to arrive at any 
specific brightness that can be consid- 
ered representative of all conditions. 
One method is to record the variation in 
integrated or average-picture brightness 
for a typical film and to determine the 
mean brightness over an extended 
period of time. However, the range of 
average brightnesses, especially the mini- 
mum values, are of importance. 

A typical record for a black-and-white 
film is shown in Fig. 2. The film used 
included photographs of almost com- 
pletely white areas to extremely dark 
night scenes and can be considered to be 
representative. In order to make the 
record of Fig. 2 more universal in its 
application, the ordinate is shown as per 
cent of clear-screen brightness. Thus, 
it is a simple matter to convert the rela- 
tive values to actual brightnesses. For 
example, in terms of the clear-screen 
brightness, the maximum average bright- 
ness recorded for the lightest scene was 
about 25%; the minimum brightness 
was 1.0%; and the mean value for the 
entire film was about 10%. Therefore, 
when the clear-screen brightness is 15 ft- 
L, the picture brightnesses are approx- 
imately 3.8 maximum and 0.1 5 minimum 
with a mean of 1.5 ft-L. It is interesting 
to note that these values compare favor- 
ably with those obtained by Logan. 2 

A similar record taken with an indus- 
trial color film gave a mean brightness of 
about 5% of the clear-screen brightness 
with maximum and minimum values of 
16% and 1%, respectively. For a clear- 
screen brightness of 15 ft-L, these 
brightnesses are a mean value of 0.75, a 
maximum of 2.4, and a minimum of 0.15 
ft-L. Obviously, there will be quite a 
wide variation among films. However, 
these brightnesses appear to be within 
the range of what is obtained in repre- 
sentative theaters. 



Sylvester K. Guth: Surround Brightness 



217 




r-r-r-7-/' / i 



h-l MINUTE-^ 




Fig. 2. A record illustrating the variation in integrated or average bright- 
ness of a typical motion picture in terms of the clear-screen brightness. 



E 




SURROUND 



PROJECTOR 
MIRRORS 



-OBSERVER 




E 




SCREEN 



BORDER 




Fig. 3. The experimental arrangement used for determining the desired 
border and surround brightness when viewing projected pictures. 



Experimental Arrangement 

In order to isolate and to control inde- 
pendently the brightnesses of the various 
areas in the visual field, the experimental 
arrangement illustrated in Fig. 3 was 
adopted. This is a modified scale model 
of a theater in which 1 in. equals 1 ft. 
The screen was 20 in. wide, thus corre- 
sponding to a 20-ft screen. The observ- 
ers were located at a distance of six 
times the screen width from the plane of 
the screen, or a distance of 120 in. 



Immediately surrounding the screen was 
a transilluminated diffusing glass, the 
brightness of which could be adjusted by 
the observers. This area corresponds 
generally to the area on a stage surround- 
ing a motion picture screen and is 
termed the screen border. Between the 
observer and the screen was a panel, the 
brightness of which could be inde- 
pendently controlled. The observer 
viewed the projector screen through a 
rectangular aperture in the panel. This 



218 



September 1951 Journal of the SMPTE Vol. 57 



aperture was ot such a size that the trans- 
illuminated screen surround could be 
seen by the observer. This arrangement 
enabled control of the two surround 
brightnesses without permitting any 
stray light to reach the screen. While 
this experimental arrangement does not 
duplicate exactly the visual situation of a 
theater, it is considered to be sufficiently 
typical for the present purposes. 

In the present investigation, which 
was intended only to be exploratory, 
clear-screen brightnesses ranging from 
1.1 to 60 ft-L were used. These include 
brightnesses that are obtainable with 
various types of projection equipment 
such as highly efficient projectors used at 
a relatively short projection distance, 
opaque projectors, slide-film projectors, 
etc. The brightnesses were obtained 
with a standard 16-mm projector in 
which were used lamps of 200, 300 and 
750 w for screen brightnesses of 11, 25 
and 60 ft-L, respectively. By means of 
a neutral-density filter, these bright- 
nesses could be reduced to one-tenth of 
these values for a lower range of 1.1, 2.5 
and 6 ft-L. These clear-screen bright- 
nesses corresponded to mean picture 
brightnesses ranging from 0.1 to 6 ft-L. 

The observers viewed the motion pic- 
ture and, for each value of clear-screen 
brightness, adjusted the brightness of the 
border until they deemed it most desir- 
able for viewing the projected picture. 
Their judgment was based upon viewing 
comfort and upon the appearance of the 
projected pictures. A group of five 
observers made a series of five observa- 
tions on each of two sittings for the vari- 
ous screen brightnesses. Each observer 
was permitted as long a period to make 
each observation as he felt necessary. 
Each series of observations included 
representative portions of the motion 
picture. 

Experimental Results 

Influence of Screen Brightness. The av- 
erage brightnesses of the border selected 
by the observers are plotted in Fig. 4 for 



clear-screen brightness ranging from 1.1 
to 60 ft-L. The observed data for view- 
ing motion pictures are represented by 
the open circles. These points can be 
represented by a straight line, indicating 
a linear relationship between the loga- 
rithms of the clear-screen brightness and 
the selected border brightness. Since 
the average-picture brightness is approx- 
imately one-tenth of the clear-screen 
brightness, the scale at the top of Fig. 4 
illustrates the average-projected-picture 
brightnesses for corresponding clear- 
screen brightnesses. The picture bright- 
ness is a more representative value, since 
it can be considered as the brightness to 
which the eyes are adapted. 

A similar investigation was conducted 
with a typical black-and-white slide 
film. The solid dots indicate the av- 
erage border brightnesses selected by 
two of the observers for four screen 
brightnesses, ranging from 1 to 20 ft-L. 
These values check very well with those 
obtained with motion pictures. In 
other words, the fact that the observer is 
viewing a still or motion picture does not 
seem to influence his decision regarding 
the most suitable border brightness. 
Similar results were obtained with a 
color film. 

It was found that the surrounding 
screen brightness had no significant 
effect upon the selection of the border 
brightness, provided that it was equal 
to or less than the latter. None of the 
observers desired a zero surround bright- 
ness. The general preference was about 
one-half the border brightness. All who 
viewed the projected pictures in the ex- 
perimental situation were unanimous in 
indicating that the border brightness 
was of greatest importance. Therefore, 
the following discussion is based pri- 
marily upon the border brightnesses 
selected by the observers for the various 
screen brightnesses. 

The desirable border brightness is not 
a simple function of the clear-screen or 
average-picture brightness, but is ex- 
ponential, and may be represented by: 



Sylvester K. Guth: Surround Brightness 



219 



AVERAGE PICTURE BRIGHTNESS, FOOTLAMBERTS 



BORDER BRIGHTNESS, FOOTLAMBERTS 
o P p p p p p _- N 

' ru u> ^ f o* o o o o 


1 0.2 0.3 0.4 0.5 0.6 0.8 1 2 3456 






























































































x^ 






























^>s 






























Jx 


X"^ 




























.-x 


x^ 




























X-" 


x"^ 
























X* 


X* 


x 


x"^ 
o 




















^ 


^ 


Lx- 
























^o 


x^ 


























^ 
































































2 3 4 5 6 8 10 20 30 40 50 6( 



CLEAR SCREEN BRIGHTNESS, FOOTLAMBERTS 

Fig. 4. The relationship between desired border brightness for various clear-screen 
and average-picture brightnesses. The open circles and solid dots represent observed 
values obtained with a motion picture and slide film, respectively. 



B = 0.16 
or B = 0.46 



(1) 
(2) 



where B, and P are the border, clear- 
screen and mean-picture brightnesses, 
respectively. A simple approximation 
is that the border brightness is equal 
to the square root of the screen (or pic- 
ture) brightness multiplied by a con- 
stant. In terms of average-picture 
brightness, the desired border brightness 
is indicated to be about one-half of the 
square root of the picture brightness. 

It may be of interest to compare the 
above equations with one developed from 
data obtained in an earlier investigation 
of comfortable brightness relationships in 
interior lighting. 3 The relationship be- 
tween the brightness, B, of a light source 
and the brightness, F, of the adapting 
field was found to be: 



B = 302 



(3) 



In the three equations, the brightness of 
a light source or luminous area outside of 
the region of a visual task is expressed as 
a function of the brightness to which the 
eyes are adapted. The coefficient is 
dependent upon the criterion, the visual 
sensation being studied and other experi- 
mental factors. However, the similarity 
between the exponents is particularly 
significant and illustrates a common 
basis for the two investigations. Since 
most visual functions follow well-estab- 
lished laws and patterns, it should be ex- 
pected that similar relationships would 
be obtained. 

The ratio between the border and pic- 
ture brightnesses is a variable one. For 
example, when the picture brightness is 
0.2 ft-L (corresponding to a clear-screen 
brightness of 2 ft-L), the indicated border 
brightness is 0.22 ft-L. This is approxi- 
mately equal to the average-picture 
brightness. However, when the picture 



220 



September 1951 Journal of the SMPTE Vol. 57 



brightness is 2 ft-L, the desired border 
brightness is 0.63 ft-L or about one- 
third of the average-picture brightness. 
In other words, relatively lower border 
brightnesses are desired for higher pic- 
ture brightnesses than for the lower pic- 
ture brightnesses. This is understand- 
able, since an important factor is the 
total luminous flux directed toward the 
eye by the area surrounding the screen. 
Furthermore, the eyes become progres- 
sively more sensitive to brightness differ- 
ences as the adaptation brightness is 
increased. Therefore, relatively lower 
border brightnesses will be selected for 
the higher picture brightnesses. Never- 
theless, these indicated desirable border 
brightnesses are considerably higher than 
those indicated by other investigators. 2 - 4 

It is emphasized that the technique 
used in this investigation eliminated the 
factor of stray light upon the screen. 
These relatively high border and sur- 
round brightnesses may be impractical in 
existing theaters. Nevertheless, these 
results do indicate that under ideal 
conditions, higher brightnesses are de- 
sirable. They should be obtainable in a 
properly designed auditorium. 

Stray Light. In the usual auditorium, a 
limiting factor which governs the per- 
missible surround brightness is the 
amount of stray light reflected upon the 
screen. Therefore, a brief investigation 
was made to determine the amount of 
stray light which would produce a just 
barely perceptible effect upon the pic- 
ture quality. A small source of light, 
mounted on the rear of the surround 
screen, was variable and controlled by 
the subject. This source provided a 
variable amount of stray light upon the 
picture screen. The observer viewed 
the projected picture, simultaneously 
varying the amount of stray light until he 
deemed it to be a maximum without 
affecting the quality of the picture. 
This was investigated with two picture 
brightnesses. When the picture bright- 
ness was 0.50 ft-L (clear-screen bright- 
ness equal to 5 ft-L), it was found that a 



stray-light brightness of about 0.07 ft-L 
produced no effect upon the picture. 
For a picture brightness of 3 ft-L (30- 
ft-L clear-screen brightness) the stray 
light could be increased to 0. 1 5 ft-L. 

Referring to Fig. 4, it is seen that the 
border brightness for a picture brightness 
of 0.50 ft-L is 0.33. Thus, the stray- 
light brightness is about one-fifth of the 
border brightness. A similar ratio was 
found for the picture brightness of 3 ft-L, 
where the desired border brightness was 
0.76 ft-L and the permissible stray light 
was 0.1 5 ft-L. 

Color Film. A similar brief investigation 
was made with a color film. While the 
one used may not be exactly representa- 
tive of the usual production films, it 
does make possible a qualitative appraisal 
of desired border and stray-light bright- 
nesses. The average-picture brightness 
was found to be about 5% of the clear- 
screen brightness, which is half of the 
average-picture brightness of the black- 
and-white film. This is lower than that 
found by Logan, 2 whose measurements 
indicated a higher average-picture 
brightness for color film than for black- 
and-white film. The results obtained 
with two observers indicated that the 
border brightness desired when viewing 
the color film corresponded to that 
obtained for the black-and-white film. 
In other words, it appears that the border 
brightness is a function of the average- 
picture brightness and that viewing color 
pictures has no measurable effect upon 
the desired brightness. 

On the other hand, it was found that 
stray light upon the screen was more 
effective for color film than for black- 
and-white film. For equal picture 
brightnesses, the maximum tolerable 
stray light for viewing color film was 
about one-half that found to be tolerable 
for black-and-white film. These results 
are logical and to be expected. The 
shading and blending of colors and their 
contrasts are important factors in the 
appearances of projected color pictures. 
On the other hand, a black-and-white 



Sylvester K. Guth: Surround Brightness 



221 



picture involves a range of neutral 
values which are merely shifted slightly 
to lighter tones by the stray light. For 
example, in the latter case, for an 
average-picture brightness of 1 ft-L, it is 
assumed that the white and black 
brightnesses are 5 and 0.05 ft-L, re- 
spectively. The tolerable stray light for 
this condition would be about 0.10 
ft-L (one-tenth of the average picture 
brightness). Calculated values of con- 
trast between the black and white areas 
without and with stray light are 99% 
and 97%, respectively. Similar calcu- 
lations for other picture areas yield 
correspondingly small changes in con- 
trast. In other words, the stray light 
selected as maximal tolerable produces 
too small a change in contrast to be sig- 
nificantly visually effective. Calcula- 
tions for color pictures would be con- 
siderably more complex since they 
would have to involve a consideration of 
color change as well as a change in 
brightness. The former probably is the 
reason for a lower tolerance of stray 
light when viewing color pictures. 

Conclusions 

The relationships between average- 
picture brightness, border and surround 
brightnesses, and the stray light make it 
possible to predict or to predetermine 
the conditions that are expected to be 
most satisfactory in any theater. A 
simple rule would be to raise the border 
and surround brightness to the value 
that will not produce an excessive level 
of stray light upon the screen. Of 
course, the brightness of the border 
should not exceed that found desirable 
for the available average-picture bright- 
ness. For example, for a typical theater, 
if the clear-screen brightness is 10 ft-L 
and the average-picture brightness is 
1 ft-L, the border brightness should 
be about 0.45 ft-L, but the stray light 
should not produce a brightness greater 
than 0.09 ft-L. 

The values of border and surround 
brightnesses indicated by this investiga- 



tion are somewhat higher than those pub- 
lished by others. Logan, for example, 
has suggested a surround brightness of 
0.10 ft-L for an average-picture bright- 
ness of 1 ft-L. 2 This is about one-fifth 
of the value determined in the present 
investigation. Others have reported sur- 
round brightnesses of the order of 0.05 
ft-L to be desirable. 4 A review of the 
limited literature on the subject indicates 
that most of the values have been based 
upon empirical attempts to apply data 
obtained with experimental and en- 
vironmental conditions that are not 
directly applicable to the viewing of 
projected pictures. Nevertheless, there 
is the common conclusion that some 
brightness is required in motion picture 
theater auditoriums. 

Another important aspect of bright- 
ness in viewing areas is the sources which 
produce the low brightnesses on the 
border, walls, ceiling and floors. At the 
low visual adaptation levels these sources 
and any other areas of relatively high 
brightness must be kept to a minimum in 
order for them not to be distracting or 
even uncomfortable. A method has 
been developed for determining the 
tolerable brightnesses of sources, such as 
aisle lights, bright areas of walls, fixtures, 
etc. In essence, they must be reduced in 
brightness and area so that their visi- 
bility does not compete with the visi- 
bility of the projected picture. The per- 
missible brightnesses of such areas is a 
function of the size of the source or 
bright wall area, its position in the visual 
field and the average-picture brightness. 
This method has been described in detail 
elsewhere. 3 ' 5 While it was not de- 
veloped for the projected picture prob- 
lem, the general principles involved 
should be applicable to any visual en- 
vironment. 

There are other factors which may 
have an important influence upon the 
final accepted or desirable surround 
brightnesses. These include, especially, 
the psychological factors which govern 
the mood of, and impressions gained by 



222 



September 1951 Journal of the SMPTE Vol. 57 



the viewers. In other words, the actual 
brightness level used should enhance the 
illusions being created by the motion 
picture. Theoretically, at least, the 
viewer is asked to place himself in the 
actual situation being created on the 
screen, be it the hot sunlit desert or 
the dark mysterious passageways of a 
haunted house. Environmental bright- 
nesses must enhance and not destroy 
these effects. Thus, there are many 
aspects to the problem of providing the 
surround brightnesses for viewing the 
projected pictures. Ultimately, all of 
them must be investigated before their 
individual importances in any situation 
can be evaluated. Perhaps a semi- 
variable control system will be necessary. 
Whatever is required should be deter- 
mined by carefully conducted investiga- 
tions rather than empiricisms or opinions. 
It is emphasized that the investiga- 
tions and results presented in this paper 
are exploratory. A primary purpose 
was to develop a technique that would 
enable observers to make considered 
appraisals of the environmental bright- 
nesses in an experimental situation that 
approximated actual viewing condi- 
tions. Since the observers used in these 
studies have been used in a number of 
earlier investigations, and were selected 
as being representative, it is believed that 
the brightnesses selected by them are 
indicatory of the levels that are desirable. 

References 

1. Matthew Luckiesh, "Brightness engi- 
neering," Ilium. Eng., vol. 39, pp. 75-92, 
Feb. 1944. 

2. H. L. Logan, "Brightness and illumina- 
tion requirements," Jour. SMPE, vol. 
51, pp. 1-1 2, July 1948. 

3. Matthew Luckiesh and S. K. Guth, 
"Brightnesses in visual field at border- 
line between comfort and discomfort 
(BCD)," Ilium. Eng., vol. 44, pp. 650- 
670, Nov. 1949. 

4. L. A. Jones, "Interior illumination of 
the motion picture theatre," Trans. 
SMPE, pp. 83-96, May 1920. 

B. O'Brien and G. M. Tuttle, "An ex- 



perimental investigation of projection 
screen brightness," Jour. SMPE, vol. 26, 
pp. 505-517, May 1936. 
5. Sylvester K. Guth, "Comfortable bright- 
ness relationships for critical and casual 
seeing," Ilium. Eng. y vol. 46, pp. 65-75, 
Feb. 1951. 

Discussion 

0. W. Richards: I was wondering if 
you'd care to make any comment on how 
the color temperature of your surround 
lighting should compare with the border 
lighting? 

S. K. Guth: In this investigation we 
were not particularly concerned with the 
spectral quality of the border lighting. 
However, we did use filters over the lamps 
used for the border brightness and used 
special combinations of fluorescent lamps 
for the surround brightness so that the 
color would be as unobtrusive and neutral 
as possible. Both could be considered 
so-called white and differences were in- 
conspicuous. Any significant difference 
between, for example, the relatively lower 
color temperature of filament lamps 
(3000 K) and the relatively higher color 
temperature of daylight (6000 K) would 
have to be investigated. I would think 
that for a typical black-and-white film 
the color of light for the border and sur- 
round is not nearly as important as it 
obviously would be for color film. It may 
be a function of the actual brightness to 
which the surround should be adjusted 
for optimal viewing conditions. It is 
possible that one color temperature will be 
desired for higher screen brightnesses, 
and another one for lower screen bright- 



Anon: I recall from several years ago 
that the Windermere Theater, on the 
Cleveland East Side, was a theater where 
auditorium illumination was on the high 
side compared with most theaters. Pos- 
sibly you people have done some experi- 
mental work there. I was wondering if 
there were any theaters that you could 
point out or that you had in mind that 
do use a border brightness of somewhere 
around the figure that you quoted, that 
is, where, for example, with 10 ft-L from 
the screen you had a border brightness 
of about 0.5 ft-L? 

Mr. Guth: I am not familiar with any 



Sylvester K. Guth: Surround Brightness 



223 



such theaters. Since I started thinking 
about this problem I have been very 
conscious of the border brightnesses and 
the surround brightnesses, but I haven't 
come across any that I would judge were 
quite that high. I have seen some of 
the theaters in Cleveland that seemed to 
have a somewhat higher border brightness 
than others, but I made no measurements. 

Anon: I was thinking that it might be 
very interesting to actually see something 
like that, and if you could convince some 
neighborhood theater in Cleveland, they 
would experiment a little bit and I am 
sure there would be enough people in 
Cleveland glad to work with you on that. 

Mr. Guth: It would be interesting to 
make such experiments. Ultimately, only 
full-scale investigations can give us the 
final answer regarding the desirable 
surround and border brightness. 

Ben Schlanger: We have designed several 
theaters in which we have relatively high 
levels of illumination around the screen, 
by the synchronous method. Mr. Logan 
has had the opportunity to see one of 
them and I believe he refers to this example 
in his paper. 

W. W. Lozier: I have two questions, 
Mr. Guth. One, your observations were 
all made at a point corresponding to the 
back of the average theater. I wonder 
how they might be changed for a person 
sitting up in the middle of the auditorium 
area or toward the front? 

Mr. Guth: I don't have any actual data 
on that particular phase of it, though 
several observers did sit at various distances 
from the screen for a few observations. 
We found that with shorter observation 
distances the surround brightness became 
less important. However, the border 
brightness still remained important because 
of its proximity to the picture area. This 
brief test indicated that the border bright- 
ness was about the same, regardless of 
the observation distance. However, this 
should be confirmed by observation 
distances. 

Dr. Lozier: Another question you relate 
this border brightness that the observer 
shows to the average-picture brightness. 
Do you have any information on what 
their preference was on picture brightness? 
Was any preference expressed on that? 

Mr. Guth: This is, of course, another 



aspect of the problem. With the available 
conditions, we obtained clear-screen bright- 
nesses up to 60 ft-L, or an average-picture 
brightness of 6 ft-L. The preferred clear- 
screen brightness was discussed by the 
five observers and by others who viewed 
the test conditions, but did not participate 
in the test. They all preferred the higher 
screen brightnesses something closer to 
25 ft-L. I personally liked the 60 f-tL 
clear -screen brightness. 

Dr. Lazier: In a theater with borders and 
surrounds covering as great a solid angle 
as you used, and with the high brightness 
you used, would there not be reflected in 
the audience area considerable light which 
would allow distraction? 

Mr. Guth: The stray light from very 
high surround and border brightness 
may provide objectionable brightnesses in 
the audience area. This illustrates some 
of the practical problems that must be 
solved by studies in actual theaters. 

0. E. Miller: I'd like to ask Mr. Guth 
if, in his experiment?, he noticed any 
tendency to change the type of illusion 
that was created from the type that you 
get with no illuminated border around the 
screen? The reason I ask this is because 
I was involved in a few experiments some 
years ago with illuminated borders and 
have done some work in print illumination 
and transparency illumination, which 
seem to show that with an illuminated 
border the mode of appearance of the 
picture actually changes from that of a 
real scene to make it appear as if you 
were looking at a print. In other words, 
the actual mode of appearance changes. 

Mr. Guth: That is correct if the border 
brightness is too high. The appearance 
of the picture and the created illusion 
were among the criteria used by the 
observers. They felt that if the border 
brightness was too high it affected the 
appearance of the picture. Even though 
there was no stray light upon the projected 
picture, the high border brightness did 
destroy the intended illusion. If they 
held the border brightness below a certain 
point, it had no noticeable effect. Of 
course, when one goes from a complete 
blackout to some brightness, an immediate 
change is obtained. However, over quite 
a range of brightnesses, there didn't seem 
to be too much effect upon the picture. 



224 



September 1951 Journal of the SMPTE Vol. 57 



Photometric Factors in the Design 
of Motion Picture Auditoriums 



By HENRY L. LOGAN 



The photometric factors in designing the visual environment in a motion pic- 
ture theater to promote the comfort, enjoyment and safety of the audience are 
discussed. The dependency relationship of screen surround and house 
brightnesses to screen brightnesses is explained. Optimum relationships are 
given and suggestions made for the practical execution of the recommendations, 
including the locations of lighting units and the shaping of the auditorium 
walls and ceilings. 



JL HE PHOTOMETRIC factors of impor- 
tance in the motion picture theater are 
the screen brightnesses with film running 
and their relationships with all the other 
brightnesses in the field of view that are 
necessary to promote the visual comfort, 
enjoyment and safety of the audience; 
and the brightness relationships without 
film running and full house lighting. 

As all the difficulties arise with the 
former and not with the latter, this paper 
will be confined to the situation that 
exists with film running. 

It will be found that a brightness dis- 
tribution that accomplishes the goals 
just mentioned requires special handling 
of the screen and its adjacent surround, 
some modifications in the shape of audi- 
toriums, predetermination of the per- 
centage of light reflected from each part 
of the auditorium interior (and hence, 
determination of finishes) and precise 



Presented on May 2, 1951, at the Society's 
Convention Screen Viewing Factors Sym- 
posium, at New York, by Henry L. Logan, 
Holophane Company, Inc. (Illumination 
Service), 342 Madison Ave.. New York 17, 
N.Y. 



control of the light emitted from the 
lighting equipment. 

Up till now, the writer has had the 
impression that most motion picture 
theaters have been designed for their 
effect on the observer with full house 
lights on rather than for their effect 
when film is running. 

With film running, motion picture 
screens average from 1 to 3 ft-L bright- 
ness. If we set the brightness relation- 
ships to meet the upper figure, we reduce 
the sensitivity of the eye to the darker 
portions of the film, even if we so light the 
theater that no house light can get back 
to the screen to reduce its contrasts. 
With auditoriums as they now exist, an 
overlay of diffused light on the screen is 
inevitable, which is one reason why 
house lighting is so little used when film 
is running. 

Actually we are driven to take the 
least brightness that occurs on a black- 
and-white film as our starting point. 
This is about 0.04 ft-L and is the same 
brightness that Spragg has shown to be 
the minimum for satisfactory visual 
performance and safety. 



September 1951 Journal of the SMPTE Vol.57 



225 




Fig. 1. Field of view of a patron seated in the standard observer's position, 

showing how the surround brightness 30 above the line of sight can be as much 

as six times the screen brightness by virtue of the position index relations. 



Brightnesses located off the axis of 
vision have a lower-discomfort effect 
than similar on-the-axis brightnesses, as 
shown by the position-index data of 
Luckiesh and Guth, 1 and Harrison. ia 
Thus, the brightness of the surround 
adjacent to the screen can be greater 
than 0.04 ft-L without impairing the 
keenness of vision directed at the screen, 
and without introducing distraction. 

For example, at a point 30 above the 
center of the screen the position index is 
3, and if the line of sight is directed at 
the center of the screen, which has a 
night-scene running of 0.04 ft-L, the 
point 30 above the screen can have a 
brightness of 3 X 0.04 ft-L, or 0.12 ft-L, 
in order to produce a response equal to 
that caused by 0.04 ft-L screen bright- 
ness, provided the areas occupied are 
about equal (see Fig. 1). 

The latest work of Guth (see the pre- 
ceding paper in this JOURNAL) shows 
that acceptable off-axis brightnesses can 
be twice as great when the observer is 
engaged in purposeful seeing, than when 
he is looking at random. As there is no 
doubt that an observer looking at run- 
ning film has his attention deeply en- 



gaged, the surround brightness at this 
point, 30 above the axis, can safely be 
2 X 0.12, or about 0.25 ft-L. This 
should permit both keen vision and a 
high degree of visual comfort under the 
condition of minimum screen brightness 
common today. 

Thus, the brightness of the screen 
surround can begin with 0.04 ft-L at the 
screen edge and increase gradually, in 
accord with the position indices for 
critical seeing, as we proceed away from 
the screen along walls and ceiling. 

The areas occupied by the bright- 
nesses are important and in practice the 
position indices, when used to guide per- 
missible surround brightness, must be 
changed by a factor to compensate for 
differences in area of screen and the 
strips of surround brightness. 

This is quite consistent with the writ- 
er's earlier findings, 2 which gave a level 
of 0.1 ft-L as the permissible maximum 
brightness within 30 of the observers' 
line of sight. 

Earlier in this discussion it was stated 
that we are driven to take the least 
brightness, that occurs long enough to 
measure on a black-and-white sequence, 



226 



September 1951 Journal of the SMPTE Vol.57 



as our starting point. This is because 
the next logical criterion would be the 
overall average brightness of the darkest 
running film, or 1 ft-L, and it would 
lead us into detrimental surround bright- 
nesses. 

Theoretically it would permit a screen 
surround brightness of 6 ft-L (3X1X2) 
at the previously mentioned 30 point. 
Against that we have the definite finding 
of Jones 3 that a brightness of 3 ft-L is the 
highest that can be tolerated toward the 
front of an auditorium. 

Recent research 4 shows that visual 
comfort for 100% of the audience is about 
J of tolerance (meaning by tolerance, the 
comfort-discomfort threshold). There- 
fore, the maximum comfortable screen 
surround brightness would be 1 ft-L or 
only f of the figure we arrive at by using 
the overall average brightness of the 
darkest running film. It is safest, there- 
fore, to stick to the criterion previously 
discussed, namely, the lowest brightness 
that occurs long enough to measure in a 
black-and-white sequence. 

Coming to the rest of the auditorium, 
recent work by Guth, 5 Petherbridge and 
Hopkinson 6 (and its development by the 
writer) shows that higher brightnesses are 
desirable in other parts of the auditorium 
than was previously thought. 

Before proceeding to a discussion of 
these brightnesses, it might be well to 
point out that acceptable screen sur- 
round brightnesses can be secured by 
utilizing the reflected light from the 
screen, in the fashion developed by 
Schlanger. The method consists of 
framing the screen in a recess of sloping 
reveals that are bathed in light from the 
screen. These reveals start at the edges 
of the screen, from which the black 
frame margin is absent, and slope out- 
ward toward the remainder of the audi- 
torium. Schlanger has carried this idea 
even farther, and has sloped all his audi- 
torium surfaces so they favorably receive 
light from the screen and reflect it into 
the house. This has the effect of main- 
taining the adaptation level of the eyes 



SCREEN 




SCHLANGER METHOD 

Fig. 2. Plan view of the proscenium 
and auditorium showing the relation 
between reveals and screen recom- 
mended by Schlanger. 




SCREEN 

Fig. 3. Plan view of proposed reveal 
lighting arrangement, with light sources 
behind screen. 



fairly close to that established by the 
screen, so that it is possible for a member 
of the audience to look all around such an 
auditorium, with the film running, and 
see comfortably well. Of course, high 
light-reflection factors are necessary, 
which restricts the range of decoration 
that can be used and gives the interior a 
somewhat severe aspect when house 
lights are on and film not running. 
Nevertheless, these interiors do give one 
the feeling that one is in an auditorium 
successfully designed for the showing of 
motion pictures to full advantage, and 
they impart a feeling of security to the 
observer that is lacking in most motion 
picture theaters. 

The screen surround can also be 
properly lighted if the screen is set for- 
ward of similar reveals. The reveals, 
then, are lighted independently from 
sources behind the screen, either synchro- 
nously, varying along with screen bright- 
ness, or at a fixed level. For the fixed 
case, the reveals remain at the same 
brightness, independent of the fluctu- 



Henry L. Logan: Photometric Factors 



227 




EQUIVALE 



SIZES OF SERRATIONS 
CAN VARY TO SUIT 
DESIGNERS DESIRES 



Fig. 4. Plan view of proposed 
system of serrations to prevent 
light reflection on to screen. 

ations of screen brightness, and so must 
be keyed to darkest screen conditions, as 
explained. However, to prevent an 
overlay of light from the reveals onto the 
screen, the screen should be level with 
the front edges of the reveals, instead of, 
as in Schlanger's use of reveals, level 
with their back edges. 

Returning to the subject of bright- 
nesses in other parts of the auditorium, 
the sides of the auditorium at the pro- 
scenium end can start with a brightness of 
0.25 ft-L, or, if the position indices do not 
permit, a lower value increasing to 0.25 
ft-L which should be continued for 
about two-thirds the length of the audi- 
torium. The walls of the back one- 
third can safely have a brightness of 0.5 
ft-L. 

The ceiling brightness should follow 
in the same way; 0.25 ft-L from the 
proscenium arch back for two-thirds of 
the ceiling, rising to 0.50 ft-L at the rear. 

Brightness on the floor should be con- 
fined to the traffic aisles and the cross- 
overs. Where aisle lights can be prop- 
erly located and shielded from the eyes 
of the patrons, they provide a satisfactory 
solution. Another solution is down- 
lights located and designed so as to light 
the aisles and crossovers only, and not 
spill light onto the audience. Floor 




brightnesses can start at 0.25 ft-L at 
front of auditorium, gradually rising to 
1 ft-L on the rear crossover. 

However, brightnesses at these levels 
will put a sufficient overlay of diffused 
light on the screen to interfere seriously 
with its clarity, unless the light is pre- 
vented from getting back to the screen. 

One way to prevent it is to serrate the 
walls and ceilings; one face of each 
serration should be turned toward the 
audience and have a high light-reflection 
factor; the other face of each serration 
should be turned toward the screen and 
given a reflection factor of about 20%. 
These serrations can have various shapes, 
but a simple dogtooth section will work 
well. 

In a rectangular auditorium both faces 
of the serrations would tend to be smaller 
toward the screen end, with the side fac- 
ing the audience, larger toward the rear; 
while in an auditorium where the walls 
sloped in to meet the proscenium, the 
side of the serrations that faced the 
audience would be larger near the pro- 
scenium. 

Various rhythms of size and shapes of 
the serrations are possible, depending 
upon the creative ability of the designer 
and the limitations in shape of the 
auditorium in question. 



228 



September 1951 Journal of the SMPTE Vol. 57 



By using an absorbing finish on the 
faces of the serrations that face the 
screen, and reflecting finishes on the 
opposite faces, the walls can be lighted 
directly from the ceiling by lighting 
equipment running along and close to the 
walls. This equipment can be con- 
cealed by a variety of methods. 

The ceiling will receive sufficient light 
by diffusion from the walls, but to have 
satisfactory brightness the reflecting 
faces of the ceiling serrations should be 
given a higher reflection factor than the 
reflecting faces of the wall serrations. 
However, they can be given a lower 
reflection factor if they are lighted inde- 
pendently from the walls. One way of 
doing this would be to make a horizontal 
break in the walls, say one-third down, 
providing a concealing ledge within 



which lighting equipment of the proper 
size and performance characteristics 
could be placed to light the ceiling indi- 
rectly. Such equipment would have to 
have perfect control as spill light on the 
walls should be avoided. 




WALL UGHTING WALL LIGHTI NG FROM 

FROM CEILING CEILING WITH CEILING 

LIGHTING FROM WALL 

Fig. 5. Wall and ceiling lighting meth- 
ods for desired surround illumination. 



100000 
50000 



20000 
10000 



5000 



n 2000 
^ 1000 

2 




.0001 



4 6 10 20 40 



.001 .01 .02 04.06 .1 .2 .4 .6 I 2 

SIZE (Q) OF SOURCE ('/. OF VISUAL FIELD) 

Fig. 6. Visual Comfort Chart The comfort discomfort threshold relations 

in terms of light source brightness, size and adaptation brightness. 

(Copyright 1951 Holophane Company, Inc.) 



Henry L. Logan: Photometric Factors 



229 



Finally, both the balcony face and the 
rear auditorium wall should be given the 
same reflection factor as the dark sides of 
the serrations, so that these surfaces, 
which face the screen, will not diffuse 
significant quantities of light to the 
screen. 

If an observer placed himself at the 
screen in an auditorium designed in this 
fashion, and looked into the house, he 
would see only the dark sides of the 
serrations, and, with the exception of the 
lighted strips of floor in the aisles, the 
auditorium would appear dark. 

On the other hand, if he went into the 
auditorium and faced the screen, he 
would see a well-lighted interior having a 
brightness distribution that gave him the 
same response as the darker sequences of 
the pictures. As he looked away from 
the screen, the auditorium would appear 
still brighter, and he would find it easy to 
look away from the picture and back 
again, in much the same way as you 
find it easy to look out of your living- 
room window onto your lawn and back 
to the interior of the room again, when 
daylight is coming through the window. 

In both cases, the brightness distribu- 
tion and level is such that visual adapta- 
tion is not significantly changed in 
moving the line of sight from the screen 
into the auditorium, or from the window 
into the living room. The sensitivity to 
the pictures would remain just as unim- 
paired as does your sensitivity to what 
you can see through the window, when 
sitting in your living room under the 
conditions described. The equipment, 
shapes of surfaces and finishes have to be 
worked out with great precision to 
accomplish the desired effects, as the 
effects occur only if control of the light is 
complete. 

Colors of finishes must be selected on 
the basis of reflection factor and neu- 
trality of observers' response. In the 
light of MacAdam's work (see his paper 
earlier in this JOURNAL), care must be 
taken that the colors selected for the 
immediate screen surround do not dis- 



tort the reception of Technicolor and 
Kodachrome in the eye. The aim is to 
provide a neutral surround to subordi- 
nate all elements in the theater to the 
projected image. 

The entire screen surround and theater 
interior should be designed with modern 
illuminating engineering techniques and 
data borne in mind. Lighting pro- 
posals for theater interiors can be 
analyzed and carefully checked by the 
flux analysis method and evaluated with 
newly-developed visual-comfort criteria 
(shown in Fig. 6), to insure that the 
proposed interior will be found visually 
comfortable by 100% of an audience. 
In short, a complete design technique is 
now available that will permit experi- 
ments to be investigated on paper, with 
the outcome of the various proposals 
rather definitely determined at the paper 
stage, instead of at the client's expense 
after the theater is finished. 

References 

1. M. Luckiesh and S. K. Guth, "Bright- 
nesses in visual field at borderline be- 
tween comfort and discomfort," Ilium. 
Eng., vol. 44, pp. 650-670, Nov. 1949. 

la. W. Harrison and P. Meaker, "Further 
data on glare ratings," Ilium. Eng., vol. 
42, pp. 153-179, Feb. 1947. 

2. H. L. Logan, "Brightness and illumina- 
tion requirements," Jour. SMPE, vol. 
51, pp. 1-12, July 1948. 

3. L. A. Jones, "The interior illumination 
of the motion picture theatre," Trans. 
SMPE, pp. 83-96, May 1920. 

4. H. L. Logan and A. Lange, "The 
evaluation of visual comfort data," pre- 
pared for presentation at 1951 National 
Conference of Illuminating Engineering 
Society, Washington, B.C. 

5. S. K. Guth, "Comfortable brightness 
relationships for critical and casual 
seeing," Ilium. Eng., vol. 46, pp. 65-75, 
Feb. 1951. 

6. P. Petherbridge and R. G. Hopkinson, 
"Discomfort glare and the lighting of 
buildings," Trans. Ilium. Eng. Soc. 
(London), vol. XV, No. 2, pp. 39-79, 
1950. 



230 



September 1951 Journal of the SMPTE Vol. 57 



New Approaches Developed by Relating Film 
Production Techniques to Theater Exhibition 

By BENJAMIN SCHLANGER and WILLIAM A. HOFFBERG 



A larger screen, camera angles, factors of psychophysical vision and audi- 
torium viewing are considered relative to the development of more flexible 
screen cinematography. Screen masking, surround and auditorium environ- 
ment are also considered. 



I 



.T is GRATIFYING to report at this time 
the increasing recognition of the signifi- 
cance of auditorium and screen en- 
vironment in relation to greater film 
enjoyment. There is also now a more 
ready acceptance of larger screens. 
These developments are due to the 
increased use of color film and the 
competition of television. The dis- 
advantages of a dark auditorium and 
screen environment have become ap- 
parent due to the recognition of the 
resulting visual fatigue and the essential 
unpleasantness of blackness; color film 
accentuates this. The Symposium on 
Screen Viewing Factors, to which this 
paper is a contribution, concerns itself 
with the above scope and is in itself 
evidence of a trend. 

Since our last paper presented to this 
Society in October 1950, 1 we have made 
further studies which now enable us to 



Presented on May 2, 1951, at the Society's 
Convention Screen Viewing Factors Sym- 
posium, at New York, by Benjamin 
Schlanger and William A. Hoffberg, 
Theater Engineering and Architecture 
Consultants, 35 W. 53d St., New York 19. 



make some definite recommendations 
for a dramatic improvement in motion 
picture exhibition in theaters. We now 
propose a substantial increase in the 
size of theater screens together with a 
new use of the increased areas beyond 
present picture sizes. The added screen 
area should be devoted to peripheral and 
interpretive cinematography as well as 
occasional use of the entire screen area 
for clearly defined images. This pro- 
posed exploitation of the additional screen 
area is of intrinsic importance. 

The advocacy and use of large screens 
has a long history. However, within the 
last 20 years, improvements in film 
grain reduction, studio set lighting and 
the increase of projection light intensity 
have now made the large screen feasible. 
Certainly the novelty factor of sound 
which was introduced about 1927, when 
large screen trials were made, has now 
been .dissipated. A major fault of the 
early large screen attempts was the 
absence of a cinematography consistent 
with wide-angle viewing in theaters. 
As a result, the audience -experienced the 
annoyance of moving their eyes to follow 
the extreme positions of action and the 



September 1951 Journal of the SMPTE Vol. 57 



231 




Figure 1 



constant doubt as to whether they were 
looking at the center of concentration. 

In our opinion, the effective use of 
the large screen is made possible by 
the following suggested production and 
exhibition techniques: 

Flexible Cinematography 

By using the larger screen as a palette, 
a more flexible cinematography is made 
possible. The present aspect ratio 
(width: height) of 8.25:6.0 is a straight- 



jacket for the cinematographer since 
various scenes require varying aspect 
ratios. By the use of darker vignettes, 
the cinematographer at present can vary 
his shape but he must sacrifice valuable 
screen area, as observed by Lewis W. 
Physioc in 1931, who wrote: "Vi- 
gnetting and other effects are prohibited 
by the limited areas." 2 The use of light 
vignettes is comparatively rare because 
existing screen surround treatments are 
invariably dark. 



-New Screen- 




232 



Figure 2 
r September 1951 Journal of the SMPTE Vol, 57 



Figure 1 depicts a present screen in the 
usual dark theater as viewed from a 
distance of about 90 ft from the screen, 
which is 5 times the screen width of 
18 ft. Figure 2 is taken from the same 
viewing distance of 90 ft and shows the 
effect with a 30-ft screen; the viewing 
distance is thus 3 times the screen width. 
The size of the head in the picture is the 
same in both illustrations but Fig. 2 
illustrates a light vignette extending into 
a light screen surround and a dark 
vignette extending into a dark screen 
surround. As a result, there is no ap- 
parent aspect ratio or confining frame. 
The effects shown in Fig. 2 have hereto- 
fore been impossible to achieve. 

Synchronous, Luminous Peripheral 
Extensions 

The larger screen would be used for 
clearly defined picture content and 
vignetted as well as peripheral exten- 
sional surrounds. All of the desired 
effects would be on the 35-mm film. 
The cameraman will have designated on 
his view-finder the boundaries of clearly 
defined detail area. This area will vary 
in size and shape to suit the require- 
ments of the scene. The props, back- 
ground and people located in the 
portions beyond the clearly defined area 
will be recorded on the film only to 
establish light intensity and color, thus 
forming an atmospheric extension of the 
detailed picture. 

By the use of diminished lighting or 
increased lighting in the periphery, for 
interior shots, the outer areas are re- 
corded as vignettes which diffuse to 
light as well as dark terminations. For 
certain interior shots and most exterior 
shots, it will be more appropriate to 
use diffusing tonal extensions which 
will be obtained by placing in the 
camera or in the optical printer a filter 
which has an open area equivalent to the 
defined picture area. The above filter 
is placed at a distance from the sensitized 
film so as to establish an amount of 
diffusion which will create color and 



light intensity extension with or without 
identifiable detail. The vignettes and 
peripheral extensions would always auto- 
matically synchronize with the detailed 
portion of the picture. 

Picture Shape 

In 1929, L. A. Jones 3 made some very 
pertinent observations regarding various 
aspect ratios. He came to the conclu- 
sion that it is impossible to get a standard 
proportion which will satisfy the variety 
of forms of compositional construction. 
He found that for landscape and mass 
compositions the most favorable ratio of 
width: height ranged from 1.55 to 1.60 
but for portrait compositions this ratio 
varied from 0.88 to 1 .48. This indicates 
the great difficulty in fixing a constant 
aspect ratio in cinematography. Flexi- 
bility of shape offers a solution. Not 
only should there exist the ability to 
vary the proportions of the rectangle 
but there should also be the possibility 
of using any other shape. It is also 
significant that it is possible to dissolve 
the sense of shape by the use of luminous 
as well as darkened vignettes and thus 
achieve a "shapeless shape." 

Use of Wide Angle Lenses 

There has been a marked trend since 
1939 toward the increased use of wide- 
angle lenses in film production. Prior 
to this date, the use of a 25-mm lens with 
a camera angle of 47.5 was exceptional. 
In 1928, A. C. Hardy and R. W. 
Conant 4 stated that to avoid perspective 
distortions in theater viewing, the correct 
location is obtained by multiplying the 
projection distance in the theater by the 
ratio of the focal length of the camera 
lens to the focal length of the projection 
lens. With a camera lens of 2-in. focal 
length and projection lens of 4-in. focal 
length, as determined by present screen 
size, the best viewing position would 
therefore be at a distance from the screen 
equal to one-half the distance from the 
projector to the screen. With a 1-in. 
camera lens and 4-in. projector lens, 



Schlanger and Hoffberg: Relating Production to Exhibition 



233 



Figure 3 

the best viewing position would be at 
one-fourth the distance from projector 
to screen. The increased use of wide- 
angle lenses therefore has a detrimental 
effect on the best viewing position in the 
theater since it throws this point too 
far forward, namely about in the third 
row orchestra. 

With the recommended use of the 
larger screen, the focal length of the 
projection lens would be reduced to 
about 2.5 in. and with a 1-in. camera 
lens, the best viewing position would be 
at two-fifths of projector to screen 
distance or about the tenth row orchestra. 
The change to larger screens is con- 
sistent with the already increased use of 
wide-angle camera lenses. 

Occasional Use of Full Screen 

Although we propose that the de- 
tailed picture area will occupy varying 
amounts of the total screen area for 
the major portion of the time, it is 
possible and advisable for climactic, 
tonic and panoramic scenes to use a 
maximum of the entire screen surface. 
This occasional use of the entire screen, 
which is all produced on the film, does 
not require the expensive and cumber- 
some mechanical spreading devices for 
the screen masking. 

Effective Use of Screen Area 

It is important to observe that in 
present cinematographic practice there 
is a tendency to "play safe" by avoiding 
the use of the marginal areas of the 



tTTIf 



Figure 4 

screen. Figure 3 is intended to express 
the diagrammatic force of pictorial 
composition as influenced by the usual 
black masking and dark screen surround. 
By way of contrast, in Fig. 4 is the 
expression of the relative effect of an 
outward force which becomes possible 
with the synchronized extension in 
light, shade and hue as previously 
described. The ability to extend im- 
portant detail and effects up to the 
extreme edges of the detailed picture 
increases the effective area of the picture. 

Visual Experience in the 
Peripheral Zone 

Psychological as well as physiological 
factors must be evaluated in order to 
analyze visual experience. Little con- 
sideration has been given heretofore to 
the problem of expressing the effects 
which occur in the peripheral zone. 
Figure 5 represents the portion of the 
field of view occupied by the camera 
angle of a wide-angle lens of 1-in. focal 
length. This angle of 47.5 includes 
varying angles of peripheral experience. 
Figure 6 indicates the portion of the 
field of view of the spectator in the 
theater from the furthest and closest 
seats, as expressed by the ratio of viewing 
distance to width of picture and shown 
as 5W and 1 W. The proportion of 
the field of view occupied by the screen 
from the average viewing position is 
far less than the widest camera angle 
and occupies much too small a segment 
of the total field of view. 



234 



September 1951 Journal of the SMPTE Vol.57 




PORTION OF i&o FIELD 

OP VIEW SUBTENDED 
BY I INCH CAMERA 
LENS (WIDE ANGLE) 



Figure 5 




APPROX. FIELD OF VIEW 
OCCUPI ED BY SCREEN 



Fig. 6. Field of view in 
existing theaters. 



MAXIMUM VIEWING 
DISTANCE 




APPROX FIELD OF VIEW 
OCCUPIED BY SCREEN FOR 
PERIPHERAL EXTENSION 
C1NEMAT06KAPWY 



l 



Fig. 7. Field of view 
as recommended. 



Figure 7 indicates the proposed 
increase in screen size and its effects on 
the proportion of the spectator's field 
of view as seen from 3W and 1 W. It 
becomes evident that, with the increasing 
use of wider angle camera lenses up 
to 1-in. focal length, the screen in the 
theater should subtend an angle con- 
sistent with camera angles. A syn- 
chronized luminous field surrounding the 
projected picture, as hereinafter de- 
scribed, subtends a still greater angle 
into the peripheral zone. 

Concentration and Diffusion 
in the Field of View 

It is most significant that the portion 
of the field of view of the human eye, 
which appears less distinct and almost 
obscured, varies considerably with the 
amount of concentration experienced at 



any given moment. The angle of clear 
vision detail discernment narrows as the 
degree of concentration increases. In 
direct contrast with this, when there is 
least reason for concentration, as in a 
panoramic view, we seem to see a 
maximum of the total field in more or 
less clearly defined detail. The viewer 
is hardly aware of the slight movements 
of the eye muscles which enable him to 
encompass the panorama clearly. 

As concentration increases in intensity, 
the angle of clear vision decreases and 
the degree of diffusion of detail outside 
of this zone increases. These observa- 
tions offer the clues as to how best to 
interpret cinematographically these ex- 
periences and help to determine the 
types of vignettes and filters to be 
employed. For example, in an interior 
shot where intense concentration occurs. 



Schlanger and Hoffberg: Relating Production to Exhibition 



235 



the vignetting process will diffuse detail 
at a point close to the main interest 
and extend therefrom into areas of 
light or shadow as the scene dictates. 

Synchronous, Luminous Screen 
Surround 

Even the recommended enlarged 
screen does not occupy a sufficient 
portion of the spectator's field of view 
in the theater. The subtended angles 
to the screen at viewing distances of 
\W, 2W and 1W are respectively 53, 
28 and 19. It is therefore highly 
desirable to extend the sensation of 
luminosity beyond the screen area so 
that the resultant subtended angle of 
the total luminous field consisting of 
screen and screen surround approaches 
the subtended angle of a 1-in. camera 
lens. We have found that this screen 
surround luminosity must be synchronous 
with the light intensity of each scene 
and, with color, the hue of this surround 
must be an extension of the colors in a 
scene. 

The screen surround begins at the 
edge of the projected picture and 
extends to the audience at an angle of 
approximately 45 to the plane of the 
screen. It has a slight concave curva- 
ture toward the audience in order to 
control gradations of light shading 
which are synchronous reflections of the 
projected picture. The surface of the 
surround usually consists of a diffusive 
finish. The dimensions of the screen sur- 
round will vary with the size of the pic- 
ture and the size and shape of the audi- 
torium, similar to installations recently 
made by us in the Crown Theatre, 
New Haven, Conn., and the Shopping 
Center Theatre, Framingham, Mass. 

It is, of course, mandatory to provide 
a proper transition between the pro- 
jected screen image and the luminous 
surround because of the fuzziness, color 
aberration and image movement dis- 
cernible at the edges. We have solved 
this problem by the use of a translucent 
plastic material located so as to overlap 



the edges and to reveal a comparatively 
narrow luminous framing. This fram- 
ing successfully blends the aforemen- 
tioned defects into the luminous picture 
surround. Thus the necessity for a 
black masking is completely eliminated; 
its use would negate the effectiveness of 
the picture surround. 

Auditorium Environment 

The proposed screen size and luminous 
screen surround do not occupy a sufficient 
portion of the field of view of the spec- 
tator from the rear of the auditorium. 
It is therefore necessary to make the 
auditorium surfaces adjacent to the 
screen surround act as a transition to 
relative darkness. Fortunately, the 
tendency in theater architectural design 
has been toward the elimination of 
distracting elements on the surfaces 
visible to the audience, thus helping to 
achieve the necessary neutrality, sim- 
plicity and destruction of scale. 

Purpose and Feasibility 

1. It is highly improbable that home 
television viewing will be able to present 
the dramatic scale and impact which 
this suggested development makes pos- 
sible. An important step would thus 
be achieved toward re-establishing the 
motion picture theater as a unique 
medium of entertainment. 

2. This development provides new 
tools and techniques which help remove 
some of the shackles which have long 
hampered the cinematographer. 

3. It provides an atmospheric ex- 
tension of picture light, shade and color 
which is more closely related to visual 
experience. Certainly, the removal of 
the black surround for color pictures is 
much to be desired. 

4. It is generally conceded that the 
reduction of contrast between picture- 
light intensity and surround-light in- 
tensity will reduce visual fatigue and 
we further contend that synchronization 
of the surround and picture lighting 
will more successfully reduce this con- 
trast. 



236 



September 1951 Journal of the SMPTE Vol. 57 



5. The ability to place important 
action in remote positions of the enlarged 
screen is consistent with the objectives 
of stereophonic sound. 

6. Most existing theaters can accom- 
modate the enlarged screen. The sight- 
line clearances in some theaters will not 
include the full height of the screen 
from some of the seats but this will not 
be serious because the obstructed areas 
of the enlarged screen will usually be 
within the zones of atmospheric exten- 
sion. The enlarged screen would be 
placed as low as possible with the intent 
of destroying the rigid horizontal line 
at the bottom of the picture. Existing 
seating patterns and distance to the 
first row of seating would not have to 
be changed since the entire enlarged 
screen is used for sharply defined images 
only occasionally. 

7. The cost of adapting existing 
theaters to this system is limited to 
providing a new screen and the surround 
treatment, new projection lenses and, 
in some instances, new projection lamp- 
houses and wiring provisions. The only 
additional operating cost is the increased 
current consumption. 

8. This development does not require 
any radical change in production equip- 
ment. The minor modifications neces- 
sary to effect the vignetting and diffusing 
characteristics herein proposed should 
not be costly. 

9. Although this development lends 
itself admirably to any increase in film 
width, it is feasible with the use of 35-mm 
film since the image enlargement which 



is required is similar to many large 
screens now in use. 

10. For new film productions using 
the above techniques, it is an important 
feature that separate prints can be made 
which are adapted for use on existing 
screens by printing only the clearly 
defined image for the entire film width 
and omitting the peripheral extensions. 
It is also possible to reprint existing 
films by the use of filters in the optical 
printer to simulate the desired effects. 

The early feasibility of this proposal 
was accented in all of the above research 
and development. 

References 

1. B. Schlanger and W. A. Hoffberg, 
"Effects of television on the motion 
picture theater," Jour. SMPTE, vol. 
56, pp. 39-43, Jan. 1951. 

2. L. W. Physioc, "Problems of the camera- 
man," Jour. SMPE, vol. 17, pp. 406- 
416, Sept. 1931. 

3. L. A. Jones, Bulletin No. 410 of the 
Kodak Scientific Research Laboratory, 
Rochester, N.Y., 1929. 

4. A. G. Hardy and R. W. Conant, 
"Perspective considerations in taking 
and projecting motion pictures," Trans. 
SMPE, vol. 12, no. 33, pp. 117-125, 
1928. 

5. B. Schlanger, "Increasing the effective- 
ness of motion picture presentation," 
Jour. SMPE, vol. 50, pp. 367-373, Apr. 
1948. 

6. B. Schlanger, "On the relation between 
the shape of the projected picture, the 
areas of vision, and the cinematographic 
technic," Jour. SMPE, vol. 24, pp. 402- 
409, May 1935. 



Schlanger and Hoffberg: Relating Production to Exhibition 



237 



Report on Screen Brightness 
Committee Theater Survey 

By W. W. LOZIER, Committee Chairman 



A 



PRELIMINARY survey of 18 theaters 
by the Screen Brightness Committee in 
1947 1 disclosed interesting indications of 
theater screen illumination practice in 
this country, but was inconclusive be- 
cause the theaters covered represented 
too limited a sampling. A more ex- 
tensive survey was not carried out at that 
time because of the lack of a suitable 
meter. More recently, the General 
Electric Company placed at the disposal 
of the Committee a meter which is better 
adapted to a theater survey. Conse- 
quently, during the summer of 1950, the 
Screen Brightness Committee of the 
Society undertook a survey of screen 
illumination and related factors in 100 
representative indoor theaters. It was 
the Committee's purpose in this larger 
survey to cover a more representative 
segment of the theaters in this country 
and to obtain dependable data concern- 
ing their practices, with the underlying 
thought that observation and discussion 
of any undesirable conditions would pro- 
mote better projection. At the present 
time, results are available on 125 thea- 
ters, representing all except the South- 
Presented on May 2, 1951, at the Society's 
Convention at New York, as a preliminary 
progress report on the first 88 theaters of 
this survey, by W. W. Lozier, Committee 
Chairman, Carbon Products Service Dept.. 
National Carbon Company, Division of 
Union Carbide and Carbon Corp., Fos- 
toria, Ohio. 



east and Pacific sections of the United 
States. It is believed that these results 
would not be greatly changed by repre- 
sentative coverage of these additional 
areas. 

During the course of this survey, the 
Motion Picture Research Council be- 
came interested in carrying out a parallel 
survey in the West Coast studio review 
rooms used for viewing 35-mm pictures. 
Through their cooperation, we are able 
to include in this report the results on 1 8 
review rooms. 

Methods and Instruments 

In contrast with the previous survey, 
all of the measurements in the present 
survey were made with an objective-type 
instrument requiring no visual photo- 
metric balance. Nearly all of the 
measurements were made with the two- 
cell General Electric combination screen 
illumination screen brightness meter. 
A few measurements were made employ- 
ing a simple foot-candle meter in com- 
bination with an improvised device for 
measuring the screen reflectivity. 2 

Data forms were simplified somewhat 
from those used in the 1947 survey and 
are illustrated in Figs. 1 to 3. 

Classes of Theaters Surveyed 

The 1 947 survey was heavily weighted 
by the large downtown theaters in large 
cities. An effort was made in this survey 



238 



September 1951 Journal of the SMPTE Vol. 57 



SCREEN BRIGHTNESS COMMITTEE 
THEATER SURVEY 



THEATER 
ADDRESS 



DATE 

REPORTED BY 



PROJECTOR 1 



PROJECTOR 2 



B, 



w 



READ INTENSITY ON THE SCREEN IN FOOT-CANDLES AT THE FIVE POSITIONS 
INDICATED. "C/" AND "CjARE LOCATED jz OF H FROM EDGES AND OF W 



20 



20, 



FROM SIDES. "0" AND "/ ARE ON THE HORIZONTAL CENTER AND OF W 
FROM SIDES. "A" IS IN THE EXACT CENTER. 



SCREEN AREA 

AREA IN SQUARE FEET = H x W- (l) 

SCREEN LIGHT INTENSITY AND DISTRIBUTION 



RATIO 



SCREEN LUMEN CALCULATION 
A x 2 = 



2 

TOTAL - 

WEIGHTED AVG. - TOTAL = 

SCREEN LUMENS = (l)x (2) 



(2) 



SCREEN AREA 

AREA IN SQUARE FEET= H x W - (\ 

SCREEN LIGHT INTENSITY AND DISTRIBUTION 



2 . A 

SCREEN LUMEN CALCULATION 



2 

TOTAL = 

WEIGHTED AVG.- ~ ^ = 

SCREEN LUMENS= (l)x (2) 



(2) 



Fig. 1. Sample data form for incident screen illumination. 



to cover a wider range of types and sizes 
of indoor theaters. Figure 4 shows the 
distribution of seating capacities among 
the 125 theaters surveyed. It also 
shows the distribution of seating capaci- 
ties among the indoor theaters of the 



United States expressed both on the 
basis of percentage of theaters in various 
seating ranges and also as the percentage 
of the total theater seating capacity fall- 
ing in the different seating-capacity 
ranges. It is seen that the distribution of 



W. W. Lozier: Report on Screen Brightness Survey 



239 



SCREEN BRIGHTNESS SURVEY 

CENTER SCREEN BRIGHTNESS AND REFLECTIVITY 

(Incident Illumination) x (Screen Reflectivity) = 

(Screen Brightness) 

Method A 

When using a combination illumination and bright- 
ness meter, measure center of screen values of 
(Incident Illumination) and (Screen Brightness) and 
calculate (Screen Reflectivity) using the above 
equation. 

Method B 

/ 

When using a reflectivity meter, measure (Screen 
Reflectivity) and combine with (Incident Illumination) 
to calculate (Screen Brightness) using the above 
equation. 

PROJECTOR 1 PROJECTOR 2 
INCIDENT ILLUMINATION 

FOOT CANDLES 

SCREEN REFLECTIVITY 

PER CENT 

SCREEN BRIGHTNESS 

FOOT LAMBERTS_ 

Fig. 2. Sample data form for screen reflectivity and screen brightness. 

theaters covered in our survey corre- call for a brightness between 9 and 14 ft- 

sponds more closely to the distribution of L. The indoor theaters ranged in 

the total United States theater seating brightness from 3.4 to 53 ft-L, with 

capacity than to the distribution of approximately one-quarter below and 

number of theaters among the various about one-half within the ASA standard 

seating ranges. While the less-than- range. Two theaters which were 

500-seat theaters account for over half of equipped with highly directional "silver" 

the total number of indoor theaters, screens had a central maximum screen 

they account for only a little more than brightness in the range of 30 to 53 ft-L. 

one-quarter of the total number of seats. In the case of the review rooms, almost 

Figure 5 gives the distribution of two-thirds were within the standard 

screen widths measured thus far. All limits and most of the remaining third 

but a small fraction of the screens were exceeded the maximum limit, 
between 14 and 24 ft in width, with the 

average at approximately 18 to 20 ft. Distribution of Illumination Over Screen 

Figure 7 shows the distribution of 

Screen Brightness illumination over the screen expressed as 

The distributions of screen brightness a ratio of side-to-center intensity of inci- 

encountered with 36 review-room pro- dent illumination. Side distribution 

jectors and 245 indoor-theater projectors ranged from 40% to 94% for the indoor 

are given in Fig. 6. The present ASA theaters with approximately 85% of the 

standard limits, also shown in Fig. 6, projectors falling between 50% and 80% 

240 September 195 1 Journal of the SMPTE Vol. 57 



SCREEN BRIGHTNESS SURVEY 

PROJECTION DATA 

1. PROJECTION ANGLE 

2. ARC LAMP TYPE 

3. POSITIVE CARBON 

4. NEGATIVE CARBON 

5. ARC AMPERES 

6. ARC VOLTS 

7. PROJECTION LENS 

(a) f/ NUMBER 

(b) FOCAL LENGTH 

(c) SURFACE COATED YES _ NO 

8. TYPE OF SHUTTER 

(a) DEGREE OPENING 

9. DRAFT GLASS TYPE 

10. HEAT FILTER TYPE 

11. PROJECTION PORT GLASS YES _ NO 

12. TYPE OF POWER SUPPLY 

(a) RATING IN AMPERES 

(b) RATING IN VOLTS 

(c) OPERATING VOLTAGE 

AUDITORIUM DATA 

1. SEATING CAPACITY 

Fig. 3. Sample data form for theater data. 



distribution ratios. The most frequent the ratio of corner-to-center incident 

distribution ratio fell between 60% and intensity. Corner distributions are, in 

70%. each case, approximately 10% to 15% 

The review rooms differ radically from lower than the side distribution and 

the mdoor theaters by having a much ranged from 26% to 83%. Figure 8 

more uniform distribution of illumina- shows, however, the same basic pattern 

tion over the screen. Of the review- as Fig. 7. 
room projectors 85% produced a side 

distribution between 80% and 100%. Screen Reflectivity 

This more uniform screen distribution Less than half of the indoor theater 

reflects the review-room problem of small screens had reflectivities in the 70% to 

screen size and excess illumination; de- 80% range, typical of a matte white 

focusing the light source to produce a screen in good condition. Over 40% of 

uniform distribution is one way which the screens ranged from 70% down to 

has been used to reduce excess screen 32% reflectivity. Approximately 10% 

brightness. It means, however, that of the screens had reflectivities between 

motion pictures are viewed in these re- 80% and 100%. Five "silver" screens 

view rooms under conditions very were in the range of 150% to 250%. A 

different from those prevaling in motion total of eight "silver" screens are in- 

picture theaters. eluded in Fig. 9. 

Figure 8 gives similar information on The review-room screens, on the aver- 

W. W. Lozier: Report on Screen Brightness Survey 24 1 



60 




58.8 






DISTRIBUTION OF TOTAL NUMBER OF 


40 


- 






27.6 


U.S.A. INDOOR THEATERS 
Data from "Motion Picture Almanac" 1947-48. 


20 
LJ n 


- 








7.7 

I | r-^-, _J^ o.7 


INDICATED RANG 

S S 


- 






33.7 


APPROXIMATE DISTRIBUTION OF TOTAL 
NUMBER OF U.S.A. INDOOR THEATER SEATS 


z 




28.3 








t 20 


- 








15.7 


9 

\- 
Z 

uj o 










9.3 77 


o u 

CC 
UJ 
Q_ 

60 


- 






50.4 


DISTRIBUTION OF 125 INDOOR THEATERS 

rOVFRFn IN ^IIRWFY 


40 
20 


- 


19.2 






19.2 













16 r _L 6 _ 1 t 4.0 






Less 
than 
500 




500 
to 
1000 


1000 1500 2000 More 
to to to than 
1500 2000 3000 3000 



SEATING CAPACITY 

Fig. 4. Analysis of seating capacities of survey theaters and total 
United States indoor theaters. 



242 



September 195 1 Journal of the SMPTE Vol. 57 



25 



20 



15 



10 



o 

o 



40 r 



g 30 
z 
< 
K 

P 20 




O 



t 



23.6 



125 INDOOR THEATERS 



18.8 



15.2 



4.4 



22.4 



11.2 



12 



14 



16 



26 



18 20 22 24 

SCREEN WIDTH, feet 
Fig. 5. Distribution of screen widths covered in the survey. 



28 



30 



40.2 



23.6 



REVIEW ROOMS 
36 PROJECTORS 



27.8 



5.6 



40 r 



PER CENT OF PROJECTORS 
o o 



10 - 



ASA 







brand 
27.3 


aras 


INDOOR THEATERS 
245 PROJECTORS 








22.9 






19.6 
















10.8 


5.9 








6.1 


_J.-<L__ 








-^-n 1.0 .p^-n 



Below 
4 



4.0 6.5 9.0 11.5 14.0 16.5 19.0 21.5 
BRIGHTNESS AT CENTER OF SCREEN, foot-lamberts 
Fig. 6. Distribution of screen brightness obtained in the survey. 



24.0 Above 
24.0 



243 





REVIEW ROOMS 


62.5 




60 


36 PROJECTORS 








UJ 














i 


40 


- 








o 












g 






23.6 






< 




20 


- 












z 






8.3 






5.6 


2 


t i i 








1 



INDOOR THEATERS 


$ 40 


251 PROJECTORS 





34.5 


o 








UJ 


_ 






o 


0/1 4 




25.9 


u. 

20 














z 












LU 
O 










11.2 


o: 10 


- 










UJ 
CL 


3.9 












r~ 








0.4 


n 


i 








1 J_ 



40 



100 



50 60 70 80 90 

SIDE-TO-CENTER DISTRIBUTION RATIO, % 

Fig. 7. Range of side-to-center distribution ratios of incident 
illumination obtained in the survey. 



110 



age, tended to have lower reflectivities 
than the indoor theaters, but not as 
great a range of extremes. This may 
again reflect the problem of excess 
illumination and the fact that even a de- 
teriorated screen will produce adequate 
brightness with the small-size screens 
employed. However, if the low reflec- 
tivity is the result of deterioration, then 
such screens may also have undergone 
color change with resultant distortion of 
color motion pictures. 

Summary 

This survey of 125 indoor theaters has 
shown that the screen brightness falls 
within the recommended range for a 
little over half of the projectors, but that 
almost one-quarter of the theaters are 
below the recommended standards. The 
distribution of illumination over the in- 



door theater screens ranges from very 
uniform to extremely nonuniform. 
Screen reflectivity for the indoor theaters 
ranges from values typical of screens in 
good condition all the way down to 
values representing over 50% deteriora- 
tion. 

The West Coast review rooms gener- 
ally show screen brightness within or a 
little above the recommended standards 
for indoor theaters. However, the re- 
view rooms differ from indoor theaters in 
having exceptionally uniform distribu- 
tion of illumination over the screen. 
Review-room screen reflectivities show a 
lower average value than, but not nearly 
as great a spread of extreme values as, 
the indoor theater screens. 

Compared to the 1947 preliminary 
survey, the present one shows an even 
wider range of screen brightness values, 



244 



September 1951 Journal of the SMPTE Vol.57 



INDICATED RANGE 

ro <Tv 

D 


- REVIEW ROOMS 
36 PROJECTORS 

2.8 


19.4 


55.6 


19.4 








2.8 



-^ 
o 



</> 

oc 

8 

O 

^ 30 
o 

K 

o. 



ro 
o 



. 
o 



INDOOR THEATERS 
251 PROJECTORS 



29-2 



12.4 



2.0 



16.5 



11.2 



0.8 



20 



30 40 50 60 70 80 90 

CORNER-TO-CENTER DISTRIBUTION RATIO, % 

Fig. 8. Range of corner-to-center distribution ratios of incident 
illumination obtained in the survey. 



100 



110 



but only about one-half as great a pro- 
portion of theaters below the recom- 
mended minimum brightness. Other 
factors studied, such as side and corner 
screen distribution ratio, cover approx- 
imately the same ranges as observed in 
the earlier survey. The screen reflec- 
tivities extend over a much wider range, 
including both some exceptionally low 
values and also a number of "silver" 
screens of extremely high reflectivity. 

Recommendation 

It is expected that the results of this 
survey will assist in the formulation of an 
eventual Committee recommendation 
for improvement of projection practice in 
theaters. In the meantime, however, 
it is believed that better attention to de- 
tails of operation and maintenance can 
reduce the wide range of screen bright- 
ness observed and eliminate many of the 



extreme values. It can also eliminate 
many of the highly nonuniform distribu- 
tions of illumination over the screen and 
thereby remove some of the objectionable 
conditions prevalent. 

The findings of this survey in the West 
Coast review rooms are being considered 
by the Motion Picture Research Council 
and West Coast studios in relation to 
their program of improving review-room 
practices. 

Acknowledgments 

The Screen Brightness Committee 
and the Society are indebted to many 
people for assistance in the conduction of 
this survey. Theater projectionists, and 
their organization the IATSE, various 
trade publications and theater managers 
have been most cooperative in making 
their facilities and assistance available to 
us. Particular thanks are due to C. W. 



W. W. Lozier: Report on Screen Brightness Survey 



245 



REVIEW ROOMS 



47.2 



18 SCREENS 








40 


- 






36.1 


30 


- 










20 


- 














11.1 








10 


- 




















5.6 





g INDOOR THEATERS 

* 40r 120 SCREENS 



43.8 



30 



20 



10 



22.9 



12.9 



4.6 



1.7 



9.1 



4.2 



0.8 



30 



40 



90 



50 60 70 80 

SCREEN REFLECTIVITY, % 
Fig. 9. Range of screen reflectivities obtained in the survey. 



100 150 
to 250 



Handley, C. E. Heppberger and P. D. 
Ries of the National Carbon Company, 
A. J. Hatch of Strong Electric Corp. and 
C. R. Underhill of RCA for supervising 
and carrying out much of the survey 
work in the different areas of the United 
States. The Motion Picture Research 
Council took the initiative in obtaining 
the data on the West Coast review 
rooms. Without the fine cooperation of 
these individuals and groups, this survey 
would have been difficult if not im- 
possible. 



References 

1. E. R. Geib, Chairman, "Report of 
Screen Brightness Committee," Jour. 



SMPE, vol. 50, pp. 260-273, Mar. 1948. 
2. W. W. Lozier, Chairman, "Screen 
Brightness Committee Report," Jour. 
SMPTE, vol. 54, pp. 756-757, June 
1950. 

The Committee 

W. W. Lozier, Chairman 



Herbert Barnett 

H. J. Benham 

F. E. Carlson 

M. H. Chamberlin 

E. R. Geib 

L. T. Goldsmith 

L. D. Grignon 

A. J. Hatch, Jr. 

L. B. Isaac 

W. F. Kelley 



F. J. Kolb 
W. F. Little 
L. J. Patton 
Leonard Satz 
J. W. Servies 

B. A. Silard 
Allen Stimson 

C. R. Underhill, Jr. 
H. E. White 

A. T. Williams 

D. L. Williams 



246 



September 1951 Journal of the SMPTE Vol.57 



Light Source for Small-Area High- 
Speed Motion Picture Photography 

By RICHARD I. DERBY and ARTHUR B. NEEB 



An illuminant which may be of interest to others working in this field 
has been assembled to give extremely high intensity for small-area use. 



w, 



ITH THE ADVENT of the G.E. No. 

750R-40 lamp designed for use primarily 
in high-speed motion picture photog- 
raphy, a large number of lighting prob- 
lems have been greatly aided or solved. 

In this laboratory, a lighting problem 
arose in which an area of about 2 to 3 
sq in. was to be illuminated with such 
intensity as to obtain a field depth of 
about 2 in. at the minimum subject-lens 
distance. The light source to be de- 
scribed consists of one lamp and allows 
the use of Super X (not XX) film with a 
normal exposure index of 32 tungsten at 
//10 using a 102-mm lens and a film 
speed of 3120 frames/sec, with a subject 
of medium reflectance (about 30%). 

The source simply consists of one 
sealed-beam Par 64 No. 4560 G.E. lamp 
normally used as an airplane-wing light 
for illumination during night landing. 
The 28-v, 600-w lamp receives its power 
through a 20-amp variable transformer 
set at 30 to 33 v; this will no doubt de- 
crease the lamp's normal life of 25 hr. 

In conjunction with the lamp, a 6-in. 

A contribution submitted July 11, 1951, 
by Richard I. Derby and Arthur B. Neeb, 
Research Dept., General Mills, Inc., 2010 
E. Hennepin Ave., Minneapolis 13, Minn. 



planoconvex condenser lens, borrowed 
from an Omega type DII enlarger, was 
used. With the transformer set at some 
low voltage, the lamp was set up at about 
3 to 4 ft from the subject while the con- 
denser was aligned at 6 to 1 in. from the 
subject according to the desired dimen- 
sion of the spot and its intensity. Full 
voltage was applied only during actual 
exposure. 

The lamp was mounted easily in a 
short metal tube of the proper diameter, 
with a narrow flange rolled in on one 
end, against which the lamp is held by a 
Bakelite strip. The strip was fitted 
across the open end of the tube and 
attached by means of spring clips and 
pins. A mounting bracket spot-welded 
to the tube allows the assembly to be 
placed on a standard lamp stand. The 
condenser lens used with the lamp is 
fastened in a tube with a split retainer 
ring holding the glass against a flange 
rolled into the end of the tube. 

A mounting bracket is fastened to the 
assembly so that it can also be used on a 
stand. 

One must naturally take into con- 
sideration the great amount of energy in 
the form of heat which will impinge on 



September 1951 Journal of the SMPTE Vol.57 



247 




Fig. 1. Setup using the PAR 64 bulb and a condenser. The voltage to the bulb 
is controlled by a 20-amp variac as shown. 



the subject during exposure. Many 
machining operations, where moving 
metal parts dissipate the heat, as well as 
clear plastics, which do not generally 
absorb a damaging amount of heat 
during the short exposure interval, can 
be photographed with this light. Small, 
rapidly moving subjects which pass 



through the illuminated area are, of 
course, a natural for this light source. 

Exceptionally clear, crisp pictures 
can be obtained with this lamp because 
of the smaller lens opening and finer- 
grained films its use permits. 

Figure 1 shows the setup using the 
Par 64 bulb and a condenser. 



248 



September 1951 Journal of the SMPTE Vol. 57 



Dynamic Transfer Characteristic of 
a Television Film Camera Chain 

By W. K. GRIMWOOD and T. G. VEAL 



The relation between kinescope luminance and the illuminance on the mosaic 
of the iconoscope can be measured under operating conditions by the use of 
specially prepared slides or 16-mm films. One or more small areas in any 
selected scene are replaced by areas of uniform density. A series of slides or a 
complete film consists of a series of pictures which are all identical except for 
the density of these measuring areas. The television chain is adjusted for 
satisfactory reproduction of the scene. Measurements of the illuminances on 
the iconoscope in the aforementioned areas are then plotted against measure- 
ments of the kinescope luminances in the corresponding areas. 

A number of transfer-characteristic curves are shown as examples of the 
effects of such variables as the density of the picture background, the shading 
control settings and the illuminance level. The differences between still and 
intermittent projection are illustrated by a set of transfer curves. Another 
group of curves shows the transfer characteristic of the photographic process, 
the transfer characteristic of the televising process, and the transfer charac- 
teristic of the combined film-television process. 

Because of the dependence of the transfer characteristic upon the nature of 
the scene, no single characteristic can be considered as representing the per- 
formance of an iconoscope film camera chain. 



-L HE TERM "transfer characteristic" paper is concerned only with a film chain 

is taken here to define the relation be- consisting of a motion picture film or 

tween the illuminance on the television slide projector, an iconoscope camera, 

pickup tube and the corresponding a camera control and a studio monitor, 

luminance of the kinescope. The adjec- The calculation of transfer character- 

tive "dynamic" is used to indicate that istics from published iconoscope and 

the transfer characteristics are measured kinescope curves is not a very satisfactory 

under actual operating conditions. This procedure; while the kinescope charac- 
teristics are well defined, the iconoscope 

Communication No. 1421 from the Kodak response cannot be defined by a single 

Research Laboratories, presented on Octo- curve. Further, the published icono- 

ber 17, 1950 at the Society's Convention e d h - h 

at Lake Placid, N.Y., by W. K. Grimwood . 

and T. G. Veal, Kodak Research Labora- illumination levels as may be used in 

tory, Rochester 4, N.Y. practice. For example, the RCA Tube 

September 1951 Journal of the SMPTE Vol.57 249 



Handbook curve of the RCA Type 1850-A 
Iconoscope ends at 20 ft-c; this is be- 
tween one-fifth and one-fortieth the 
illumination that may be used in actual 
operation. Because of the uncertainty of 
the iconoscope characteristic, it was felt 
that measurements might best be made 
while the television film chain was 
carrying a picture image. There is not, 
unfortunately, a single transfer charac- 
teristic. Each adjustment of pedestal, 
gain, shading or kine brightness results 
in a different characteristic. In general, 
these controls were set for best picture 
quality, a criterion which is rather vague 
and is subject to considerable variation 
between individuals. 

Slide Projection 

In order to measure the television 
transfer characteristic, we have used a 
method developed by J. G. Streiffert, 
of the Kodak Research Laboratory. 



One or more perforations are punched in 
a slide of any suitable subject. Pieces 
punched from a film of uniform density 
are cemented into these perforations. A 
series of such slides are fabricated, the 
inserted "densities" being different in 
each slide. The slides are essentially 
identical prints from the same negative 
(except for the inserted densities), and 
the perforations are punched from a 
template so that they will be in the same 
area of the picture in all slides. One 
slide from a group of twenty-eight is 
shown in Fig. 1. Each slide in this 
group has three measuring areas: the 
spot in the white dress will be called spot 
W, the one in the black dress, B, and the 
one in the gray dress, G. The spots are 
f in. in diameter and comprise about 1 % 
of the useful area of the Retina-Camera 
size slide. While the area of the spots is 
too small to affect the response of the 
iconoscope to the picture signals, the 




Fig. 1. Sample slide, showing measurement areas. 
250 September 1951 Journal of the SMPTE VoL 57 



spots do have a noticeable effect under 
some conditions. If the spot densities are 
either higher or lower than the highest 
and lowest densities, respectively, in the 
picture, the average luminance of the 
picture on the kinescope will shift 
slighdy. For the series of slides illus- 
trated by Fig. 1, the highest and lowest 
densities were approximately 2.6 and 
0.3, respectively. Above and below 
these densities there may be some ques- 
tion as to the accuracy of the data. 

The slide projection used for these 
measurements was a Kodaslide Projec- 
tor, Model 2A, equipped with an Ektar 
//4.5 enlarging lens and masked .to 
project the 3 : 4 picture ratio used in 
television. The television equipment 
was an RCA film camera chain using a 
Type 1850-A Iconoscope and an RCA 
Type 1816P4 Kinescope. Relative 
illuminances and luminances were meas- 
ured with a Welsh Densichron. The 
Densichron modulates the photoelectric 
current by subjecting the electron stream 
to a 60-cps magnetic field. When the 
kinescope luminance is measured, this 
modulating field is not necessary, since 
the light is already modulated by the 
television 60-field scanning, so that a 
switch was installed in the Densichron 



to "open-circuit" the modulating field. 
In order to make the Densichron probe 
less sensitive to position when the kine- 
scope luminance is measured, the probe 
was modified so as to accept only a 
narrow cone of light. The phototube 
used has an S4 surface. 

In general, the measuring procedure 
consists in adjusting the camera controls 
until a satisfactory picture is obtained, 
using for this purpose a slide with no 
spots. The video level is maintained at 2 v 




00 



0.5 



--2.5 



-3.0 



-20 -1.5 -10 

Log illuminance (relative) 



0.0 



Fig. 2. Slide projection, showing 
effect of surround. 



SpotG 




-50 



> 

ol 



-2.5 -2.0 -1.5 -10 -05 0.0 

Log illuminance (relative) 




-25 -20 -15 -10 -05 

Log illuminance (relative) 



00 



-0.5 



Fig. 3. Transfer characteristic, no shading; left, slide normal; right, slide reversed. 
Grimwood and Veal: Dynamic Transfer Characteristic 251 




Fig. 4. Sample slide, showing gray background, and measurement areas. 



peak-to-peak. Measurements are then 
made of the kinescope luminance in the 
spot areas, using the Densichron probe in 
contact with the face of the kinescope. 
The series of slides are measured and the 
spot luminances plotted against icono- 
scope illuminance. Illuminances are 
measured by projecting the slide series 
onto one of the standard Densichron 
probes. The probe is placed at the same 
distance from the projector as the icono- 
scope mosaic and so located tfiat the spot 
area covers the probe aperture. A 
Macbeth Illuminometer is used to 
measure reference levels of illuminance 
and luminance. All of the slide curves, 
unless otherwise noted, were taken at an 
illuminance level, with no film in the 
projector, of about 800 ft-c. 

A typical set of curves is shown in Fig. 
2. This figure also illustrates the effect 
of the luminance of the area surrounding 



the measuring spot. The controls were 
set for what was judged to be good pic- 
ture quality in a darkened room. Zero 
level on the luminance scale is about 12 
ft-L. The shading controls were ad- 
justed until the monitor cathode-ray 
oscilloscope showed a uniform white 
level. Note that spot W, which is sur- 
rounded by an essentially white area, 
does not have the luminance range of 
the other two spots. This effect may be 
decreased by use of the shading con- 
trols, but may not be eliminated. A 
similar effect, due to lens flare, is meas- 
urable upon direct projection of a slide. 
With the projection equipment used for 
these tests, the lens flare effect is, how- 
ever, negligible over the range of lumi- 
nances reproduced by the kinescope. 

Figure 3 shows curves taken with no 
shading signals. The two sets of data 
are comparable, the only difference be- 



252 



September 1951 Journal of the SMPTE Vol.57 



- -0 



Spot 




-25 



-2.0 -15 -1.0 -0.5 

Log illuminance (relative) 



-I 5 



-30 5 



-25 



SpalB 




-1.5 



-2.00 



-2.5 -2.0 -1.5 -1.0 -0.5 

Log illuminance (re la t i ve ) 



Fig. 5. Slide projection, showing 
progressive change of curvature and 
maximum slope of transfer charac- 
teristics as background changes from 
black (above, left) to gray (above, 
right) to white (right). 

tween them being that that on the right 
was taken with the slides reversed right 
and left, so that spot W, normally on the 
left side of the picture, is, in the right part 
of Fig. 3, on the right side of the picture. 
Comparison of the two sets of curves 
shows only small differences between the 
two B curves and between the two G 
curves, but fairly large differences in 
shape and slope between the W curves. 

A second series of slides was prepared 
with the objective of illustrating the 
effect of the picture background upon the 
transfer characteristic. These slides, one 
of which is reproduced in Fig. 4, were 
prepared from photographs of a girl in 
evening dress seated before a plain cur- 
tain backdrop. Three negatives were 
taken, in one of which the backdrop was 
black, in another, gray, and in the third, 
white. One measuring spot, designated 
as B, was located in the background area 
and another, designated as S, in the 
subject's shoulder. The transfer charac- 
teristic was measured on the same equip- 
ment and by the same technique as used 



Spot 




Spots 



-0.5 



-10 



-2.0 



-25 



-25 -20 -15 -1.0 

Log illuminance (relative) 



in conjunction with the first series of 
slides. Pedestal, gain, brightness, and 
shading controls were adjusted for the 
most acceptable picture for each of the 
three backgrounds. The measured 
transfer characteristics are shown in Fig. 
5. Zero on the luminance scale of Fig. 5 
is 6 ft-L. These curves exhibit a pro- 
gressive change of curvature and of 
maximum slope as the background is 
changed from black to gray to white. 
The transfer characteristic for the white- 
background pictures has a nearly linear 
central portion and pronounced high- 
light and shadow compression. The 



Grimwood and Veal: Dynamic Transfer Characteristic 



253 




2.0 l.S i.O 

Original density 



Fig. 6. Transfer characteristic of 16-mm 
motion picture process. 




Log illuminance (relative) 



Fig. 7. Television transfer characteristic, 
16-mm film projection. 



luminance range and the slope of tHe 
transfer characteristic are much lower 
than those for the gray or the black back- 
grounds. 

16- Mm Film Projection 

The technique used in measuring the 
television transfer characteristic for 16- 
mm film projection is similar to that 
Used for slide projection, except that the 
measuring areas were produced photo- 
graphically. A negative of the same 
scene as was used for the slide measure- 
ments was enlarged from a usable size of 
2f by 3| in. to 11 by 14 in. One-inch 
holes were punched in this positive 
transparency in the same locations as 
were used for the spot areas in the slides. 
The transparency was laid on an 
illuminator and photographed with a 1 6- 
mm camera, the holes being filled with 
1-in. disks of neutral nondiffusing densi- 
ties. A series of 16-mm photographs 
were taken, a different value of neutral 
density being used for each section of the 
1 6-mm film. A contact print of the 1 6- 
mm negative was projected onto the 
iconoscope mosaic by the Eastman Model 
250 Projector. With no film in the gate, 
the illuminance on the mosaic was 260 
ft-c. Luminances and illuminances were 



measured with the Densichron in a man- 
ner similar to that described in connec- 
tion with the slide measurements. 

Since the 16-mm films are made by 
photographing a transparency in which 
there are inserts of known densities, data 
are available on the overall motion pic- 
ture characteristics (including camera 
and projection optics) as well as on the 
television characteristic. Figure 6 shows 
the photographic characteristic and Fig. 
7 is one set of curves of the television 
characteristic. The differences be- 
tween the curves of Fig. 6 are due to un- 
evennesses in illuminance in the taking 
and projection processes. These un- 
evennesses do not enter into the curves 
of Fig. 7; here, the differences are 
chiefly associated with shading. Note 
that in this example the television charac- 
teristic has a greater range of luminances 
than the photographic process character- 
istic. Not all this range is usable, how- 
ever, because the low luminance levels 
are normally masked by room lighting. 
While the characteristic of Fig. 7 may 
give somewhat poorer picture qual- 
ity than that of Fig. 6, because of the 
greater highlight compression, either 
characteristic should result in acceptable 
tone rendition. The product of these 



254 



September 1951 Journal of the SMPTE Vol. 57 




.of 



i 5 



2.0 



25 



2.0 1.5 i.O 

Original density 



0.5 



0.0 




-0.5 -1.0 -1.5 

Log.illuminonce (relative) 



-20 



Fig. 8. Overall transfer characteristic. 

16-mm motion picture process televised Fig. 9. Television transfer characteristic, 



by iconoscope film camera chain. 



16-mm negative film projection. 



two characteristics is, as may be expected 
from Fig. 8, far from satisfactory. The 
spread between the three curves of Fig. 8, 
especially in the shadow region, is not 
particularly significant, since it may be 
largely corrected by adjustment of the 
shading controls. In a television film 
chain using only linear amplifiers, little 
can be done to correct the severe high- 
light compression of the overall transfer 
characteristic. Readjustment of the 
operating controls to improve tone rendi- 
tion in the highlights merely results in 
poor tone rendition in some other portion 
of the tone scale. 

Figure 6 should not be taken to repre- 
sent the optimum tone reproduction of 
the motion picture process. It does, 
however, illustrate the kind of character- 
istic which gives good picture quality. 
That the tone reproduction character- 
istic of the motion picture process is 
curved rather than linear, is not due to 
the technical inability to produce, within 
reasonable limits, a linear characteristic. 
The overall tone reproduction curve of 
the motion picture process is the result of 
the motion picture industry's years of 
practical experience. Any assumption 
that the relation between screen lumi- 



nance and scene illuminance should be 
linear for either motion picture or tele- 
vision reproduction is not justified by 
this experience. If a television screen is 
to be viewed under conditions similar to 
the viewing of motion picture screens, 
the television film chain transfer charac- 
teristic should be approximately linear. 
(Alternatively, the television character- 
istic could be curved and the film charac- 
teristic linear; this would restrict the 
television pickup to specially made 
films.) The statement that the tele- 
vision transfer characteristic should be 
linear contains the implicit assumption 
that the material to be televised is a 
motion picture of good direct-projection 
quality. It is customary, in filming 
pictures for television use, to use flatter 
lighting than for pictures taken for dis- 
tribution in theaters. Satisfactory re- 
production of such material requires that 
the relation between the logarithm of 
luminance and the logarithm of illumi- 
nance be linear, with a slope greater than 
unity. The apparent high contrast of 
the television transfer characteristics 
shown in this paper is, in part, due to the 
use of original negatives taken with low- 
contrast lighting. 



Grimwood and Veal: Dynamic Transfer Characteristic 



255 




I 

-.of 



2.0 



-2.5 




-2.5 -2.0 -1.5 -1.0 -0.5 

Log illuminance (relative) 



--15 



--2.5 



-2.5 -2.0 -1.5 -l.O -O.5 0.0 

Log illuminance (relative) 



Fig. 10. Television transfer characteristic, 16-mm film projection; 
left, shading A; right, shading B. 




-2.0? 




S 

-,.5 I 



-2.0 -1.5 -1.0 

Log illuminance (relative) 



-20 -1.5 -1.0 

Log illuminance (relative) 



Fig. 11. Television transfer characteristic, 16-mm film projection (filtered light); 
left, normal illuminance; right, low illuminance. 



It is well known that televising a nega- 
tive over an iconoscope camera results in 
better picture quality than the televising 
of a print. While there are several 
reasons for the improvement, one reason 
is a more linear transfer characteristic, 
as may be seen from Fig. 9. Figure 9 is 
from measurements on the negative 
from which the print was made for the 
measurements plotted in Fig. 7. 

Adjustment of the shading controls 



does not merely raise or lower the transfer 
characteristic relative to the luminance 
scale. Figure 10 illustrates the sort of 
change that results from even a slight re- 
adjustment of shading. The data of 
the left part of Fig. 1 were taken under 
the same conditions as the data of the 
right part, except for the shading-control 
setting. Readjustment of shading has 
left spot G practically unchanged. 
Spots B and W have been shifted upward 



256 



September 1951 Journal of the SMPTE VoL 57 




ID 5 



2 
20? 

23 



-2.5 -2.0 -1.5 -1.0 -0.5 

Log illuminonce (relative) 

(a) Shutter stationary 

Fig. 12. Television transfer charac- 
teristic, 16-mm film projection (filtered 
light). 



on the luminance scale, but at the same 
time their slope has been reduced. It 
appears to be generally true that the 
slope of the luminance-versus-illumi- 
nance curve is changed by the shading; 
in regions where shading is used to raise 
the average brightness, the slope is de- 
creased, and vice versa. 

The effect of illuminance level upon 
the transfer characteristic is illustrated 
by Fig. 1 1 . Data for both sets of curves 
were taken with color filters in the pro- 
jector condenser system. The zero of 
the illuminance scale for the left set of 
curves represents a level of 91.5 ft-c. 
For the right set of curves, zero level 
represents 91.5 ft-c attenuated by a non- 
diffusing neutral density of 0.7. Zero 
on the luminance scale is 5.6 ft-L for both 
figures. At each illuminance level, the 
television controls were adjusted to give 
what was considered to be the most 
satisfactory picture quality obtainable. 
The transfer characteristic measured at 
the lower illuminance level exhibits a 
shorter range of luminances and more 
marked highlight compression than the 
higher-level characteristic. These 




-oo 



-I 



-20 



--2.5 



-2.5 -2.0 -15 -1.0 -.5 

Log illuminonce (relative) 

(b) Shutter rotating 




oo 

-0.5 

V 
-1. 0-| 

-I 5 | 
1 

-2.6? 

-2.5 



-2.5 -20 -1.5 -1.0 -0.5 

Log il luminance (relative) 

(c) Shutter rotating, television 
controls readjusted. 



curves show only the transfer character- 
istic; to the operator, there is also a de- 
cided difference in case of shading in 
favor of the higher illuminance level. 

Still-Versus-Motion Picture Projection 

The transfer characteristics shown for 
still projection and those for motion 
picture projection cannot be compared 
directly because the picture sizes and the 



Grimwood and Veal: Dynamic Transfer Characteristic 



257 



illuminance levels were not the same for 
the two cases. It was, however, found 
feasible to make a direct comparison of 
still and intermittent projection on the 
Model 250 Television Projector. By 
placing a dichroic filter between the 
lamp housing and the synchronous 
shutter, sufficient red and infrared 
radiation was reflected so that a piece of 
heat-absorbing glass could be placed be- 
tween the shutter and the second pair of 
condenser elements. The heat-absorb- 
ing glass absorbed enough of the re- 
maining infrared radiation so that the 
film could be left stationary in the film 
gate, with the shutter stopped in the 
open position, without serious damage to 
the film. With the shutter rotating, the 
illuminance on the iconoscope mosaic 
was 92 ft-c by measurement with a Mac- 
beth Illuminometer. The illuminance, 
with the shutter stationary, was reduced 
to the same measured value by placing a 
nondiffusing neutral density in the pro- 
jection beam and slightly readjusting the 
projection lamp voltage. The transfer 
characteristics are shown in Figs. 12 (a), 
12(b) and 12(c). For all three figures, 
zero on the luminance scale is 11 ft-L. 
Figures 12 (a) and 12(b) are taken with- 
out any readjustment of the television 
controls; the figures are a direct com- 
parison of constant-versus-intermittent 
illumination. Without touching the 
brightness control, the pedestal, gain 
and shading controls were readjusted to 
give the best picture quality while 
maintaining the peak-to-peak video 
level at 2 v. Figure 12(c) is the charac- 
teristic measured after this readjustment 
of controls. It is evident that inter- 
mittent illumination is responsible for a 
large loss in contrast and luminance 
range and for a serious unevenness of 
luminance over the picture area. Most 
of this loss, but not all, is regained by 
adjustment of the controls. Although 
the curves for still and for intermittent 
projection (after adjustment of the con- 
trols) are similar in shape, the curves of 



Fig. 12(c) indicate poorer highlight re- 
production for intermittent illumination. 

Conclusion 

A number of curves have been pre- 
sented, each of which represents the 
transfer characteristic of an iconoscope 
camera and a studio monitor under 
actual operating conditions. It should 
be emphasized that these curves were 
obtained under certain specified condi- 
tions and do not furnish a firm founda- 
tion for generalizations. They have 
been useful in corroborating visual 
judgment of picture quality and of pic- 
ture defects. 

There is no single transfer character- 
istic representing the light input-light 
output relation in an iconoscope film 
chain nor can a single specification exist, 
so long as the transfer characteristic is 
a function of the distribution of the light 
transmitted by the subject material. 

Discussion 

C. R. Keith: What density steps are 
used in these tests? 

Mr. Veal: We used 0.1 density steps 
in the range of to 2.5. 

R. 0. Drew: As photographic people 
like to think of gamma, even in terms of 
television equipment, what was the over- 
all gamma of the iconoscope, kinescope 
and film characteristic that you used in 
taking these pictures? 

Mr. Grimwood: With one exception 
the curves do not include the film charac- 
teristic. Most of the curves have no 
linear portion so there is no gamma in 
the photographic sense. The maximum 
slope in the mid-portion of these curves 
is likely to be higher than that of a 
curve having a long linear region. This 
is a compromise which must be made to 
obtain some semblance of tone scale in 
the end portions of the curves. In 
addition, the slope of the transfer charac- 
teristic is partly a compensation for the 
low-contrast lighting that is frequently 
used in producing film for televising. 



258 



September 1951 Journal of the SMPTE Vol. 57 



Use of Color Filters in a 
Television Film Camera Chain 

By W. K. GRIMWOOD and T. G. VEAL 



The quality of pictures televised by an iconoscope film camera is improved by 
removing the red and infrared portions of the radiation incident upon the 
mosaic of the iconoscope. The combination of heat-absorbing glass with either 
an absorption or a reflection type of color filter can be used in the condenser 
optical system of a 1 6-mm projector. Such a combination of filters reduces the 
heat at the film gate enough to permit the film to be held stationary in the gate 
without damage to the film. The color niters improve picture sharpness, 
reduce shading requirements, and increase the signal level. The improve- 
ment in sharpness is partly an optical effect. The increase in signal level, de- 
spite the reduction of photoactive radiation, is believed to be an electronic 
effect peculiar to the iconoscope principle. 



I 



T HAS BEEN FOUND that the quality of 
pictures produced by a television film 
chain is improved if the red and infrared 
components are removed from the 
radiation incident upon the mosaic of the 
iconoscope. Experimental work with a 
number of color filters, of which the 
three curves of Fig. 1 are illustrative, 
was carried out on the Eastman 16-Mm 
Television Projector, Model 250. The 
light source of this projector is a tungsten 
lamp operated at about 3400 K. The 
greatest improvement in picture quality 
was observed when using the filter de- 



Communication No. 1409 from the Kodak 
Research Laboratories, a paper presented 
on October 17, 1950, at the Society's Con- 
vention at Lake Placid, N.Y., by W. K. 
Grimwood and T. G. Veal, Eastman 
Kodak Co., Kodak Park Works, Rochester 
4, N.Y. 



fined by curve 2 in Fig. 1. This com- 
bination of a 6-mm thickness of Pitts- 
burgh No. 2043 Glass (heat-absorbing) 
and a 3-mm thickness of Corning No. 
9780 Filter is recommended for use in 
the Model 250 Projector. Figure 2 
shows the location of the two filter 
glasses between the synchronous shutter 
and the film plane. This location 
necessitates the use of the heat-absorbing 
glass, the sole function of which is to 
reduce the infrared energy in the projec- 
tion beam so that there is no danger of 
breakage of the Corning filter from heat 
absorption. Placing the filters between 
the shutter and the film is preferable to 
inserting the filters between the projec- 
tion lens and the iconoscope, for several 
reasons. The latter choice is undesir- 
able because it injects the possibility of 
image degradation due to optical imper- 



September 1951 Journal of the SMPTE VoL 57 



259 



90 



80 



70 



60 



~ 50 



40 
30 
20 
10 




400 500 600 700 800 

Wave length m millimicrons 



900 



1000 



Fig. 1. Spectrophotometric curves of filters used in 16-mm television projector: 

Curve 1, dichroic No. 1 plus Pittsburgh No. 2043, 4 mm thick; curve 2, Corning No. 
9780, 3 mm thick plus Pittsburgh No. 2043, 6 mm thick; curve 3, dichroic No. 2 plus 
Pittsburgh No. 2043, 4 mm thick. 



Synchronous 
Shutter 

\ 



1 000 W 
Projection 
Lamp 



260 



Pittsburgh 

2043 Glass 

6 mm 



Film Gate 
X 




Projection 
Lens 



Condenser 
System 



Corning 
9780 Filter 
3 mm 



Iconoscope 
Mosaic 



Fig. 2. Eastman Model 250 Projector optical system. 
September 1951 Journal of the SMPTE VoL 57 




400 



500 



600 



700 



800 



900 



1000 



Wave length in millimicrons 



Fig. 3. Spectrophotometric curve of filters used in 16-mm projector of 100 ft-c 
illuminance. Dichroic filter plus Pittsburgh No. 2043, 4 mm thick. 



fections in the filter glass, or to accumula- 
tion of dust on the filter surfaces. The 
filter itself is more exposed to accidental 
breakage. The most compelling reason, 
however, is that when the filters are 
located in the condenser system, the film 
can be left stationary in the film gate 
(with the shutter operating) for an in- 
definite period without buckling. The 
radiant flux at the film gate is 0.55 mw/ 
sq cm, one seventeenth of the unfiltered 
value. The filters absorb about 35% 
of the energy within their passband and 
have a transmittance of 10% at 590 m/x. 
With a projector illuminance of 250 
ft-c, the loss of photoactive light by filter 
absorption is not serious, but with a pro- 
jector illuminance of the order of 100 ft- 
c, this absorption becomes a more im- 
portant factor. Furthermore, glass fil- 
ters occupy appreciable space which 
may not be available in a projector con- 
denser system. In such situations, the 
dichroic or interference type of filter is 
therefore useful. The dichroic filter not 



only has low loss in the transmitted band, 
but removes unwanted radiation by re- 
flection rather than by absorption. The 
latter property makes it possible to coat 
the dichroic filter directly on the rear 
element of the condenser optics. A dis- 
advantage of the dichroic filter is its 
band-elimination type of characteristic, 
that is, the transmittance drops to a 
level of perhaps one quarter to one half 
of 1% in the red, but at still longer 
wavelengths the transmittance increases 
rapidly. Fortunately, Pittsburgh No. 
2043 Glass has sufficient absorption in 
the region where the dichroic filter fails, 
so that the combination of this glass and 
the dichroic filter results in a satisfactory 
filter. Figure 3 shows the absorption 
curve of a dichroic filter plus a 4-mm 
thickness of the heat-absorbing glass 
(Pittsburgh No. 2043). For this com- 
bination, the 10% transmittance point is 
at 640 m/x; thus, there is less loss of 
photoactive light with this filter than 
with that described by curve 2 of Fig. 1 . 



Grimwood and Veal: Filters in a Television Camera 



261 



Figure 4 is a schematic drawing of the 
projector optical system for which this 
filter was designed. The location of the 
dichroic coating and of the heat-absorb- 
ing glass is indicated in the figure. 

For best results, the edge and bias 
lights in the film camera should also be 
filtered. Since little heat radiates from 
these light sources, the filtering may be 



done with 2-in. squares of Corning No. 
9780 or No. 9788 Filters in a 3-mm 
thickness. 

Measurements of the dynamic transfer 
characteristic, taken with and without 
filters, do not satisfactorily indicate the 
observed improvement in picture qual- 
ity. If measurements are made with 
and without filters, but with no change 



Pittsburgh 
2043- 4mm 



Dichroic 
Coating 




1000 W 
Projection 
Lamp 



Filrn Gate 




Projection 
Lens 



Synchronous 
Shutter 

Fig. 4. Projector optical system. 



Iconoscope 
Mosaic 




Fig. 5. Photographs of the monitor kinescope images. Photographs from the same 
frame of a normal 16-mm print. Left, with filters; right, without filters. 



262 



September 1951 Journal of the SMPTE Vol.57 



in the television controls, there will be a 
distinct difference in the curves. This 
is not a legitimate technique, since the 
insertion of the filters changes the signal 
level and the shading. The signal level 
increases and the contrast increases, but 
these changes may also be produced in 
the unfiltered picture by manipulation of 



the gain and pedestal controls. When 
pedestal, gain and shading have been 
readjusted to produce an unfiltered pic- 
ture which visually matches the filtered 
picture, then the transfer characteristic 
curves have been so modified that it is 
not possible to ascribe specifically any 
difference in shape to the filters. Small 
differences in the critical highlight region 




300 400 500 600 700 

Wave length in millimicrons 



800 



Fig. 6. Relative response to tungsten at 3400 K. 

I, average human eye; II, Type 1850-A iconoscope; III, chromatic aberration of 
3-in. Projection Ektar with television 12 X attachment (use right-hand ordinate scale). 




Fig. 7. Photograph of the kinescope monitor image (black-and-white) 

reproducing a picture projected from 16-mm Kodachrome original. 

Left, filtered picture; right, unfiltered picture. 



Grimwood and Veal: Filters in a Television Camera 



263 



are especially likely to be masked by 
shading-control adjustments. 

Although the effects of color filters are 
not obvious from transfer characteristic 
measurements, the effects are readily 
perceived upon visual examination. 
With filters installed in the projector and 
in the television film camera, the most 
noticeable change in the picture is a 
reduction of the haze or veil which is 
characteristic of televised film pictures, 
and an increase in picture sharpness. 
The improvement in sharpness is most 
apparent in the increased detail visible 
in highlight areas. Figure 5 is repro- 
duced from photographs of the monitor 
kinescope image. Both pictures are 
from the same frame of a normal 1 6-mm 
print. The picture on the right was 
televised without filters; that on the 
left, with filters. The television con- 
trols were adjusted to match the pictures 
visually as closely as possible for contrast 
and brightness. The left-hand picture 
is definitely sharper in appearance; 
detail is visible in the latter that is 
missing in the right-hand picture, 
especially in the hat area. 

That the improvement in sharpness is, 
in part, an optical effect, can be seen 
from Fig. 6. In this figure, curve I 
represents the spectral response of the 
average human eye to tungsten illumina- 
tion; curve II is the spectral response of 
the Type 1850- A iconoscope to tungsten 
light, as calculated from the response 
curve published in the RCA Tube Hand- 
book (extrapolated to 800 mju); and 
curve III is the chromatic aberration 
curve of the projection lens used in the 
Eastman Model 250 Projector. Visu- 
ally, this is an excellent projection lens; 
no discernible shift in visual focus results 
from the insertion of the television filters 
(Fig. 1). The eye, however, is rela- 
tively uncritical of the sharpness of the 
red and blue components of the image, 
owing to the low luminosity of these 
components and to the chromatic 
aberration of the eye. Since a con- 
siderable portion of the iconoscope re- 



sponse lies in the red and infrared re- 
gions, where the focal plane of the lens 
does not coincide with that of the green, 
it is reasonable to expect the sharpness 
of televised pictures to be improved by 
the removal of this red and infrared 
radiation. 

The most striking improvement in 
picture quality is found in the televising, 
in black-and-white, of color film such as 
Kodachrome. Figure 7 is a photograph 
of the kinescope monitor image repro- 
ducing a picture projected from 16-mm 
Kodachrome. The unfiltered picture 
on the right is much lower in contrast 
than the filtered picture on the left, 
although this represents the best match 
that could be obtained by adjustment of 
the operating controls. 

The marked improvement in the 
quality of Kodachrome pictures, when 
the projection beam is filtered, is due 
largely to the spectral characteristics of 
the image-forming dyes. Organic dyes 
are generally transparent in the infrared 
region. When unfiltered tungsten radi- 
ation is used for projection, the mosaic of 
the iconoscope is flooded with infrared 
radiation carrying no image, but to 
which there is an appreciable photo- 
electric response. A similar degradation 
of picture quality can be produced when 
projecting silver images by uniformly 
illuminating the mosaic with a small 
amount of radiation from an auxiliary 
light source. 

A major advantage in using filters is a 
decrease in shading requirements. The 
scene-to-scene changes in shading, when 
projecting motion pictures, are reduced 
to such an extent that shading readjust- 
ments are necessary only when there are 
radical changes in the distribution of 
light and dark areas in the picture. 

The improvement in shading appears 
to be associated with an increase in signal 
level. The insertion of filters in the 
Model 250 Projector is accompanied by 
an increase in the signal as indicated by 
the monitoring cathode-ray tube, al- 
though calculations from the published 



264 



September 1951 Journal of the SMPTE Vol.57 



,oo 



60 



g 40 



20 




300 



800 



400 500 600 700 

Wavelength in millimicrons 

Fig. 8. Relative response to tungsten at 3400 K. 

I, Type 1580-A iconoscope; II, iconoscope with dichroic filter and 4 mm of Pittsburgh 
No. 2043 Glass; III, iconoscope with 3 mm of Corning No. 9780 Filter and 6 mm of 
Pittsburgh No. 2043 Glass. 



spectral-response curve of the iconoscope 
show that the photoactive light is re- 
duced by the filters to only about 40% 
of the unaltered value. The increase in 
signal level is approximately 20%. 

Figure 8 shows the spectral response of 
the iconoscope to tungsten radiation at 
3400 K (curve I), the response of the 
iconoscope with the dichroic filter com- 
bination (curve II), and the response of 
the iconoscope with the glass filters 
(curve III). Although the total photo- 
active radiation is reduced by filtering, 
as shown by the relative areas of these 
three curves, the average velocity of 
primary electron emission from the 
mosaic is increased, since the velocity of 
emission is greater for the shorter wave- 
lengths. Higher average velocity should 
increase the distance between the space 
charge and the mosaic, so that fewer 
electrons are repelled by the space 
charge and fewer are lost by the space 
charge to the mosaic. It follows that 



the output level could reasonably be 
higher and the shading problem lessened 
by this action. Some improvement in 
highlight resolution could also be ex- 
pected. 

The improvement in picture quality 
resulting from the use of filters varies 
from one iconoscope to another. The 
differences in results are probably largely 
due to variations in the response to red 
and infrared, relative to the response to 
blue among iconoscopes. The edge- 
light filter which usually reduces edge 
flare has little effect with some icono- 
scopes, and has little or no effect when 
low-illuminance edge lighting is used. 
The bias-light filter normally results in a 
less critical bias-light adjustment for 
application-bar cancellation, but fre- 
quently has no appreciable effect. Fil- 
tering the projection beam nearly always 
results in a worth-while improvement in 
picture quality, but the degree of im- 
provement is less when filters are used 



Grimwood and Veal: Filters in a Television Camera 



265 



with projectors of low illuminance. 
Within the range of illuminances cur- 
rently obtained in motion picture pro- 
jection, picture quality improves with 
increased illumination; the addition of 
filters further improves the quality by 
producing a sharper picture. 

Acknowledgment 

Filters have been used in commercial 
television broadcasting by WHAM-TV, 
the Stromberg-Carlson station in Roch- 
ester, through the kindness of K. J. 
Gardner of that station, by the Columbia 
Broadcasting System station in New 
York, and by several CBS affiliates. 
We are most grateful to H. A. Chinn and 
K. B. Benson, of the Columbia Broad- 
casting System, for their cooperation in 
field trials of these filters and for their 
courtesy in passing on to us the results of 
their field experience from numerous 
filter installations. 

We wish also to acknowledge the con- 
tributions of George Koch, Development 
Dept., Camera Works, Eastman Kodak 
Co., who made the dichroic filters used 
in their experiments, and those of 
numerous members of the Research 
Laboratory staff. 



Discussion 

E. W. Kellogg: Was it necessary that the 
visible red light be removed by the filters? 
Of course, that would seem to put some 
limitations on the applicability when you 
get into color, but as you illustrated when 
reproducing a color original, I noticed that 
the transmission characteristics of the filters 
you used cut considerably in the red. 

Mr. Veal: We do remove all the red 
light. The object is to obtain optimum 
results for black-and-white television repro- 
duction. 

R. L. Carman: Is the ultraviolet cut out 
because of lens flare, fluorescence and that 
sort of thing, or is it for the same reason that 
the infrared is cut out? 

Mr. Veal: The reduction of the ultra- 
violet was not deliberate, but the filters 
used removed part of the ultraviolet radia- 
tion. 

H. M. Gurin: Has any effort been made 
to use a light source in which the red is 
absent, so that the use of filters could be 
avoided? 

Mr. Veal: The GE pulsed light source is 
widely used. With the new FT231 lamp 
it is unlikely that there would be much 
improvement when reproducing a black- 
and-white picture. The use of filters 
would be advisable when reproducing a 
color picture in black-and-white. 



266 



September 1951 Journal of the SMPTE Vol. 57 



Duplication of Color Images 
With Narrow-Band Filters 



By RODGER J. ROSS 



Outlined are some of the problems of the users of direct-positive subtractive 
color films, such as Ansco Color and Kodachrome, in producing acceptable 
duplicate images which in some cases may be third-generation reproductions. 
An experimental project will be described in which it was found that it is 
possible to produce duplicate images which may be directly compared with 
the camera originals by exposing the duplicating film with filters transmitting 
three relatively narrow spectral bands. While no attempt has been made in 
this paper to deal in any detail with the theoretical aspects of color reproduc- 
tion, a number of factors which are of great concern to the users of color 
materials have been noted particularly the establishment of visual accept- 
ance limits for color images, and the influence of processing upon the shape and 
relationship of the three-color density curves representing an image of a 
neutral wedge. 



I 



N THE NORMAL white-light printing of 
color film, deliberate alteration of the 
color balance may be employed to pro- 
duce duplicate images which are quite 
satisfactory for some purposes. In the 
hands of a skillful technician, the results 
which can be achieved in this way are 
quite surprising. For instance, large 
numbers of excellent 1 6-mm motion pic- 
ture prints have been produced by direct 
printing from the camera originals. 1 - 2 

The problems involved in the repro- 
duction of larger still transparencies are 

Presented on April 30, 1951, at the Soci- 
ety's Convention at New York, by Rodger 
J. Ross, Special Effects Div., National 
Film Board of Canada, John Street, 
Ottawa, Ontario, Canada. 



considerably more severe. Here it is 
possible for the observer to relate the 
appearance of individual colors in an 
image to objects in the immediate 
vicinity, or to make side-by-side com- 
parison of images. In addition, there is 
ample opportunity for leisurely evalu- 
ation of different image areas. 

The appearance of a color image is 
often described by the term "color bal- 
ance." This term is at best an uncertain 
indication of the characteristics of a 
color image, for it is well known that 
color balance may be influenced by 
such factors as the conditions of viewing. 
Visual evaluation, while suggesting the 
direction in which correction should be 
made, provides no indication of the 
degree of correction required, or the 



September 1951 Journal of the SMPTE Vol.57 



267 



nature and extent of the factors which 
are responsible for unsatisfactory appear- 
ance. 

In any attempt to improve the quality 
or appearance of color images, it is very 
difficult to demonstrate conclusively the 
degree of improvement that is obtained 
in a particular case. The best that can 
be done is to say that, as a result of visual 
evaluation, the image is a pleasing 
representation of the original object or 
scene, or that a duplicate image closely 
resembles the original image from which 
it was made. This might be defined as a 
process of establishing acceptance limits 
within which satisfactory images may be 
obtained. Since the eye is particularly 
sensitive to differences in colors in side- 
by-side comparisons, the acceptance 
limits established in direct comparison of 
duplicate and original color images 
might be expected to be severely re- 
stricted, as opposed to a condition under 
which an image is evaluated in respect 
to its pleasing appearance. 

The Color Sensitometry Subcom- 
mittee of this Society, in a report pub- 
lished in the JOURNAL, 3 describes the 
progress that has been made in extending 
black-and-white sensitometric proced- 
ures to the evaluation of color materials 
and color images. One of the require- 
ments of a color process might be said to 
be the reproduction of a neutral gray 
scale or wedge as a neutral image. The 
image of a neutral wedge might be 
represented by three curves on graph 
paper, derived from color density meas- 
urements on the image. Any system of 
this kind, however, must take into ac- 
count the differences in the effects of a 
color image upon the eye and its influ- 
ence upon another color material when 
duplicates must be made. There is the 
problem, too, of representing just-visible 
differences between color images of 
objects or scenes by significant quanti- 
tative differences in measurements upon 
a wedge image. Furthermore, a neutral 
image of a wedge is by no means an 
absolute requirement of a visually satis- 



factory image of a colored object. It 
should be possible eventually, however, 
to describe a color image in terms of a 
series of numbers, or as patterns upon a 
chart or graph paper, and to apply this 
information in the control of exposure 
and processing of color materials, in 
order to ensure that an image will be 
obtained within the acceptance limits 
established as a result of visual evalu- 
ation. 

The deficiencies of the dyes of sub- 
tractive color materials have been 
described in detail in the literature. In 
brief, it may be said that as the result of 
the unsatisfactory transmissions and 
absorptions of available dyes, the colors 
in duplicate images will become de- 
graded or desaturated. 4 In addition, 
the contrast of a color image must be 
relatively high to obtain satisfactory 
color saturation. 5 - 6 When a color image 
such as this must be reproduced on 
another color material with similar con- 
trast characteristics, the contrast of the 
duplicate image will be further in- 
creased. Masking has been recom- 
mended as at least a partial solution for 
these problems. While it has been 
shown that it is possible to overcome 
completely the deficiencies of the sub- 
tractive process by masking, this would 
require the use of multiple masks. It is 
seldom practical, however, to utilize 
more than one mask in duplication. 
The practical difficulties involved in 
making and registering even a single 
mask have limited the use of masking 
procedures, particularly in motion pic- 
ture printing. 

Requirements for Two Languages 

A basic problem of the National Film 
Board of Canada is the production of 1 6- 
mm color films in English- and French- 
language versions one of which must 
be printed from color masters. When 
the Technical Research Division first 
undertook a study of the problems of 
color reproduction in the autumn of 
1 947, it appeared that no worth-while 



268 



September 1951 Journal of the SMPTE Vol. 57 



contribution could be made by further 
work on conventional color-correction 
methods. The possibilities were con- 
sidered, however, of reproducing color 
film with three narrow spectral bands 
instead of white light. The idea of 
printing color film in this way was not a 
new one, even at that time. The 
Schinzels had proposed in 1937 that 
positive color prints might be made in 
this way from Agfa color negatives. 7 
Dufaycolor, an additive process, was 
being printed with three filters. 8 Since 
then, however, interest in three-filter 
exposure techniques, especially in motion 
picture printing, has increased. East- 
man Kodak has recommended recently 
that positive color prints from their new 
color negative should be produced in 
this way. Kendall was one of the first to 
propose that direct-positive subtractive 
color film might be printed with three 
filters instead of white light, and des- 
cribed a modified 16-mm step printer 
which could be used for this purpose. 9 
No attempt had been made before this 
project was initiated, however, to 
determine the most suitable spectral 
bands or the degree of improvement 
which might be obtained with this 
method of exposure. 

The results of the experimental work 
on this project over the past three years 
would indicate that this method of re- 
producing direct-positive subtractive 
color images has some important ad- 
vantages. The reproduction of indi- 
vidual colors can be improved and it is 
possible to exercise considerable control 
over image contrast. It is very difficult, 
as previously noted, to specify the exact 
degree of improvement that may be 
obtained. Since dye deficiencies are 
merely reduced and not entirely elimi- 
nated by this method of reproduction, 
duplicate images, identical with the 
camera originals, cannot be obtained. 
However, demonstration material has 
been assembled to indicate that duplicate 
images representing average objects or 
scenes may be made to fall within the 



most critical acceptance limits referred 
to previously and it is often difficult to 
select the camera original. In com- 
parisons of this kind, image contrast is an 
important factor. Although it may not 
always be necessary or desirable to do so, 
the contrast of duplicate images may be 
reduced by variation of processing until 
it is actually lower than that of the 
original, with no adverse effects upon 
the acceptance limits. 

The eye is influenced by color images 
in such a way that color arrangement is 
an important factor in obtaining satis- 
factory duplicate images. In the course 
of this project it was found that if the 
original image contains a significant red 
area, for instance, there may be some 
degradation or alteration of this area in 
the duplicate image, and the failure of 
the process to reproduce this color is 
immediately apparent. The same de- 
gree of degradation or alteration will be 
present, of course, in all duplicate images 
produced in the same way, but may not 
influence the acceptance limits. In de- 
termining the most favorable color bal- 
ance, a number of camera originals with 
widely different color arrangements 
should be selected, and with this method 
of reproduction a balance may be found 
which is satisfactory for all average scenes, 
eliminating the necessity for scene-to- 
scene correction. Further alteration of 
color balance will not as a rule improve 
the appearance of duplicates which do 
not fall within the acceptance limits. 

The filters which have been used in the 
experimental work transmit relatively 
narrow spectral bands (Fig. 1). The 
object of this exposure method is to pro- 
duce an image with each filter which is 
confined to a single layer of the dupli- 
cating film. Therefore, the transmission 
bands of the filters must be selected and 
the widths of the bands must be re- 
stricted so that this objective may be 
achieved. 

When a color image has been produced 
by exposure in a camera, it should no 
longer be necessary to consider this 



Rodger J. Ross: Duplication of Color Images 



269 



image in the same sense as an original 
scene for the purposes of further repro- 
duction, but rather as a set of three dye 
images into which the scene has been 
separated. The object in duplication, 
then, is to transfer each individual dye 
image to the corresponding layer in the 
duplicating film. Because of the unde- 
sirable transmitting and absorbing char- 
acteristics of the color-film dyes, there 
must always be more or less dye in the 
various areas in the corresponding layers 
of the duplicating film than in the three 
layers of the original image. 



40 



30 



20 



10 




(3) 



700 



400 500 600 

WAVELENGTH, millimicrons 

Fig. 1. The filters that have been 
used in the experimental work on the 
color duplication project. 



When exposure is made with suitable 
filters, the light transmitted by the 
three superimposed dye images of the 
original film will be modified to that 
which will pass through these filters 
(Fig. 2). 

The transmission of the magenta dye 
in a color film for red, green and blue is 
not sharply defined, but passes gradually 
from one color to another. For a given 
sensitivity band of the green-sensitive 
layer of a duplicating film, then, the 
effective green transmission of the 
magenta layer may be much greater than 
it might appear to be. It would seem to 
be obvious that, since the starting point 
in color degradation and distortion is to 
be found in this unwanted green trans- 
mission, considerable improvement should 
be obtained by restricting the transmis- 
sion of the magenta dye in the green 
region by means of a narrow-band filter. 

The possibility of lowering the con- 
trast of duplicate images by alteration of 
the processing times was also explored. 
It was found that the processing times 
for Ansco Color film exposed with three 
filters could be reduced by as much as 




Magenta 




(2) 



Yellow 




500 600 700 



400 500 600 700 400 500 600 700 400 

WAVELENGTH, millimicrons 
Fig. 2. Spectrophotometric curves. 

Curves indicated by (1) were supplied, in each case, by the Kodak Company as rep- 
resentative of the Kodachrome dyes. The curves indicated by (2) were calculated 
( X4)from data supplied by Kodak on the dyes and the filters selected for the three-filter 
process. The transmission of the cyan dye in the red, the magenta dye in the green, and 
the yellow dye in the blue is, of course, undesirable, and if this could be eliminated it 
should be possible to produce identical duplicate images. 



270 



September 1951 Journal of the SMPTE Vol.57 



30% from the recommended times, with 
no apparent adverse effects on the 
appearance of the duplicate images. 
Under these conditions, the contrast of 
the duplicates was somewhat lower than 
that of the original camera images. 
However, in lowering the contrast of 
duplicate images it is very important 
that the higher densities should be very 
nearly visually neutral otherwise un- 
desirable alterations in the appearance 
of the images will be introduced. 

While it was not possible in this project 
to study in detail the influence of vari- 
ations in processing times upon the color 
images, it is known that processing is a 
significant factor in determining the 
shape and relationship of the three-color 
density curves representing an image of a 
neutral wedge (Fig. 3). This aspect of 
color-image formation has received little 
attention in the literature, although the 
effects of variations in time of first de- 
velopment have been described in some 
detail by Morse. 10 

In addition, the precise control of 
color processing is not a simple matter. 11 



Slight variations in the constitution of the 
color developer will exert a strong influ- 
ence upon color images, and the influ- 
ence of a particular processing condition 
may not be the same with different color 
materials. 12 When a small quantity of 
color developer is used to process ex- 
posed film, changes in the developer be- 
tween two successive tests may be re- 
sponsible for a change in the appearance 
of the duplicate images equal to a vari- 
ation of 10% in the exposure for one of 
the filters. 

There are, of course, some practical 
difficulties in applying the three-filter 
exposure technique in the reproduction 
of color images. When the exposure 
system consists of a white-light source 
with a particular spectral distribution, 
the illumination or the exposure time 
may be adjusted so that images will be 
obtained at a level suitable for viewing or 
projection, and the spectral distribution 
of the source may be altered to obtain 
the desired color balance by means of 
voltage changes or color-compensating 
filters. With a three-filter exposure 



3.0r- 



2.0 



1.0 





I 3579 11 13 15 17 19 21 1 3 5 . 7 9 11 13 15 17 19 21 

STEPS 
Fig. 3. Color density curves on Ansco Color film. 

Left, under controlled processing conditions with which satisfactory demonstration 
material was produced, i.e., originals and duplicates which could be compared side by 
side; 

Right, conditions representative of commercial motion picture processing, with which 
it would be impossible to produce duplicate images falling within the acceptance limits 
of side-by-side comparison. 



Rodger J. Ross: Duplication of Color Images 



271 



system in which the light transmitted by 
each filter presumably affects only a 
single layer of the film, a different set of 
conditions must be fulfilled. While it is 
somewhat more difficult to establish the 
desired color balance and image level 
with an exposure system of this kind, it is 
much more flexible. For instance, tung- 
sten or daylight-type color films may be 
exposed with the same system by suitably 
adjusting the ratio of the three-filter 
exposures. For the most critical pur- 
poses, this is a precise procedure com- 
pared to the use of color-compensating 
niters. 

The method of exposure also presents 
some problems. In the reproduction of 
still images, successive exposures with the 
three filters may be made. Kendall has 
described a 16-mm motion picture 
printer 9 employing an integrating prism 
and a three-filter exposure system in 
which narrow-band filters could be used. 
A single light source could be employed 
with some means for alternating the 
filters in the light beam. A number of 
methods might be used to alter the time 




700 



or intensity of exposure through each 
filter to vary the color balance. It 
should also be possible to employ mono- 
chromatic illumination in which case the 
desired spectral lines or bands might be 
selected by filters or slits. 

The three-filter exposure system has 
been used to produce duplicates of large 
still color images that are satisfactory for 
viewing or further reproduction. A 
somewhat unusual and successful appli- 
cation for this exposure method was 
found in the production of 35-mm color- 
film strips from 16-mm motion picture 
frames. These "cine-strips" are made 
in an optical apparatus in which provi- 
sion is made for exposure through three 
filters. The color master obtained in 
this way was printed in a step printer, 
the lamphouse of which had been 
modified to expose the third-generation 
duplicates in the same manner. The 
three-filter exposure system has also been 
used successfully by the Banting and Best 
Institute, University of Toronto, to 
reproduce medical photomicrographs 
and color transparencies in which any 



Fig. 4. Chromaticity diagram giving a 
comparison of dominant wavelength and 
excitation purity of original and dupli- 
cate color patches, both of which were 
produced by exposure of Ansco Color 
film with three filters, under conditions 
which produced acceptable duplicate 
images (from International Commission 



450Xx^ 


on Illumination). 




Yellow 


Magenta 


Cyan 




Orig. 


Dup. 


Orig. Dup. 


Orig. Dup. 


)ominant wave- 
length 
.xcitation purity 
lelative brightness 


581.9 
91.00% 
36.67% 


581.5 
87.00? 
31.32? 


559. 6C 540. OC 
r o 49.7% 44.0% 
& 4.817% 3.967% 


495.5 493.0 
23.9% 33.2% 
28.65% 16.02% 



272 



September 1951 Journal of the SMPTE Vol. 57 



alteration in color or contrast is par- 
ticularly undesirable. 

The three-filter exposure method is 
not limited to the reproduction of stills, 
as has been demonstrated in the con- 
tinuous printing of film strips in a 
motion picture printer. The techniques 
of white-light release printing of motion 
picture color film, however, have been 
developed to the point where fairly 
satisfactory prints may be produced 
from good-quality camera originals. 
Any new technique which presents new 
problems might not prove to be tech- 
nically or economically practical, in 
spite of the possibility of further im- 
provements in color quality and con- 
trast. When adequate means have been 
devised to control printing and processing 
operations by means of color sensito- 
metric procedures, precise printing 
methods such as the three-filter exposure 
technique should prove to be of great 
value in improving the quality of color 
release prints. 

There is one application in motion 
picture printing in which the three-filter 
exposure technique should prove to be 
particularly useful, however. The inter- 
cutting of optical intermediates with 
camera originals is seldom satisfactory, 
and such alternatives as A & B printing, 
and special apparatus for obtaining sim- 
ple optical effects direct from the camera 
originals must be employed. Inter- 
mediates suitable for intercutting should 
match the camera originals as closely as 
possible in color balance, the appearance 
of individual colors, image level and con- 
trast. It has been shown that duplicate 
images with these desirable character- 
istics can be produced with the three- 
filter process. The problems involved in 
establishing and maintaining processing 
conditions, in order that motion picture 
intermediates with these characteristics 
may be produced consistently, are such 
that the closest collaboration with the 
processing laboratory is required. Facil- 
ities for processing lengths of film suitable 
for screening were not available for this 



project, and while considerable experi- 
mental work has been directed toward 
the production of optical intermediates, 
the demonstration material is limited to 
still images. 

Some attention was directed, in the 
course of this project, to the quantitative 
evaluation of changes in color balance 
due to variations in the three-filter ex- 
posures, but a satisfactory method for 
indicating just-visible differences in the 
appearance of duplicate images has not 
been found (Fig. 4). The nature and 
extent of correction, in terms of percent- 
age variation of the filter exposures re- 
quired to obtain the desired results, was 
estimated by visual evaluation of com- 
parison images. This is unquestionably 
a very tedious and uncertain method, 
and much experimental work is involved 
in obtaining the best possible results. 
From the standpoint of the users of sub- 
tractive color films, it would be desirable 
to find some means of establishing 
acceptance limits for color images, and of 
interpreting these limits in terms of the 
nature and extent of the variations in 
exposure and in the processing conditions 
which might be required to produce 
images consistently within these limits. 

When Ansco Color film is exposed 
with three narrow-band filters, there 
appears to be increased sensitivity to 
slight changes in the characteristics of 
the film and in processing. If this is 
true, this method of exposure might 
prove to be an advantage, in a form of 
color sensitometry, in detecting and 
evaluating film and processing variations 
of little significance under normal condi- 
tions of use. There would seem to be 
some advantage, too, in utilizing the 
three-filter exposure system to set up 
reproducible color exposure conditions 
which could be readily specified and 
which should require little maintenance. 
While variations in the spectral distribu- 
tion of a light source, now commonly ex- 
pressed in terms of color temperature, 
will influence the film whether exposure 
is made with white light or with narrow- 



September 1951 Journal of the SMPTE Vol.57 



273 



band filters, it should be possible to 
specify more precisely the characteristics 
of an exposure system in relation to the 
energy in these three bands of the 
spectrum. 

References 

1. W. H. Offenhauser, Jr., "Duplication 
of integral tripac color films," Jour. 
SMPE, vol. 45, pp. 113-134, Aug. 
1945. 

2. P. S. Aex, "A photoelectric method for 
determining color balance of 16-mm 
Kodachrome duplicating printers," 
Jour. SMPE, vol. 49, pp. 425-430, 
Nov. 1947. 

3. Report of the Color Sensitometry Sub- 
committee, "Principles of color sensi- 
tometry," Jour. SMPTE y vol. 54, pp. 
653-724, June 1950. 

4. T. H. Miller, "Masking: a technique 
for improving the quality of color re- 
production," Jour. SMPE, vol. 52, pp. 
133-1 55, Feb. 1949. 

5. R. H. Bingham, "Sensitometric evalu- 
ation of reversible color film," Jour. 
SMPE, vol. 46, pp. 368-378, May 
1946. 



6. W. T. Hanson, Jr., and F. A. Richey, 
"Three-color subtractive photog- 
raphy," Jour. SMPE, vol. 52, pp. 119- 
132, Feb. 1949. 

7. Karl Schinzel and Ludwig Schinzel, 
"Copies from Monopack Negatives," 
Das Lichtbild, vol. 12, p. 137, 1937. 
(Translated by Joseph S. Friedman, 
Amer. Photography, vol. 32, p. 439, June 
1938.) 

8. A. B. Klein, "Color cinematography," 
Chapman & Hall, London, 1939, p. 
438. 

9. O. K. Kendall, "16-mm film color 
compensation," Jour. SMPTE, vol. 54, 
pp. 464-479, Apr. 1950. 

10. H. G. Morse, "Color film exposure and 
first development timing," PSA Jour., 
Sec. B., No. 1, vol. 17, pp. 2-6, Feb. 
1951. 

11. F. C. Williams, "Current problems in 
the sensitometry of color materials and 
processes," Jour. SMPTE, vol. 56, pp. 
1-12, Jan. 1951. 

12. J. E. Bates and I. V. Runyan, "Proc- 
essing control procedures for Ansco 

Color film," Jour. SMPE, vol. 53, pp. 
3-24, July 1949. 



274 



September 1951 Journal of the SMPTE Vol. 57 



Proposed American Standard 



ALMOST FROM THE OUTSET of the motion 
picture industry, the size and shape of 
the 3 5 -mm film perforation presented a 
continuous and continuing problem. 
The Proposed American Standard ap- 
pearing on the following pages is another 
attempt to standardize a single perfo- 
ration (Dubray-Howell) for both nega- 
tive and positive film. However, this is 
not offered now as a universal perfora- 
tion to replace the two separate standards 
but rather as a third and alternate cutting 
and perforating standard. It is again 
published here for 90-day trial and criti- 
cism. All comments should be sent to 
Henry Kogel, SMPTE Staff Engineer, 
prior to January 1952 along with a car- 
bon for Dr. E. K. Carver, Chairman of 
the Film Dimensions Committee. 

This proposal and a detailed history 
of the subject were previously published 
in April 1949; however, objections were 
raised and the proposal was rejected by 
the Standards Committee on the grounds 
that a 90-day trial period was insufficient 
for a proposal of this nature. It has 
since been thrashed out in meetings of the 
Film Dimensions Committee, changes of 
a non-dimensional character made, and 
all objections overcome. Since a period 
of well over two years has elapsed, it is 
believed that a 90-day period, subsequent 
to this publication, should be adequate 
for comment. 

A brief review of the sprocket-hole 
story is provided for background infor- 
mation. 

The first attempt at standardization 
was initiated with a paper by D. J. Bell, 
published in the JOURNAL for October 
1916. He proposed a perforation hav- 



ing a width of 0.110 in., a height of 
0.073 in. and rounded sides. Within a 
few years, this "Bell & Howell" perfo- 
ration was accepted almost universally 
and was formally standardized in 1922. 
This development led in turn to a re- 
design of sprocket teeth to provide a 
greater picture steadiness with the ac- 
cepted perforation. 

However, after some time, it was 
noted that this perforation gave evidence 
of fracturing at the corners when run fre- 
quently through projection equipment. 
In 1923, (on the basis of experimental 
tests) J. G. Jones proposed a rectangular 
perforation having filleted corners, the 
same 0.110-in. width and an increased 
height, 0.078 in., to eliminate sprocket- 
tooth interference encountered previ- 
ously with the 0.073-in. dimension. 
Since this new perforation might have 
given trouble in some cameras then in 
use, its use was not recommended for 
negative films. With its adoption in 
October 1925, separate standards for 
positive and negative film came into 
existence. 

The present proposal was first put 
forth by Messrs. Dubray and Howell in 
April 1932. They claimed that it com- 
bined the advantages of both perfo- 
rations and that film so perforated could 
still be used on all existing equipment 
without alteration. This, however, 
found few supporters at the time and in- 
stead the existing rectangular perforation 
for positive film was adopted in 1 933 as 
the universal standard for both negative 
and positive film. Although this stand- 
ard was used for positive and sound film, 
it was not used for camera negative film. 



September 1951 Journal of the SMPTE Vol. 57 



275 



In 1937 the Subcommittee on Film Per- 
forating Standards proposed withdrawal 
of the 1 933 standard and adoption of the 
Dubray-Howell proposal in its place 
but without success. 

It then became apparent that estab- 
lishing a universal perforation would be 
very difficult. This left negative film 
without an official standard and conse- 
quently the old Bell & Howell perfo- 
ration, still in common use, was re-estab- 
lished as a standard for negative film. 

The issue lay dormant until some time 
in 1945 when the American Standards 
Association asked the Society of Motion 
Picture Engineers to reaffirm or revise 
the standards, in accordance with its 
policy of periodic review of all standards. 
In the reviewing process the Motion Pic- 
ture Research Council refused to approve 
the negative perforating standard and in- 
stead proposed that the whole question 
be reinvestigated and the Dubray- 
Howell perforation be reconsidered. 
The Film Dimensions Committee, there- 
fore, initiated and carried through a 
rather thorough study of the whole ques- 
tion during 1947-48. The study re- 
vealed that this perforation had a pro- 
jection life superior to the negative perfo- 
ration and only slightly less than the posi- 
tive perforation. In addition, it oper- 
ated satisfactorily in most equipment de- 
signed for either of the old perforations 
and also produced films of satisfactory 
steadiness. (For additional information 
on the studies of the Dubray-Howell per- 
forations made by the Motion Picture 
Research Council, see the January 1951 
Journal, p. 30.) 

At about this time, the registration 
problem that exists in the printing of cer- 
tain types of color release prints enters 
the picture. It is possible to solve the 
problem by the use of cine negative per- 
forations in the release prints, but then 
shortened projection life becomes a fac- 



tor. Meanwhile, two producers used 
film having the Dubray-Howell perfora- 
tion for a number of color release prints 
and obtained very satisfactory results 
when printing from standard negative 
Bell & Howell perforations. This lent 
added weight and significance to the at- 
tempts to standardize the Dubray- 
Howell perforation and, indeed, was the 
stated reason for the publication of this 
standard initially in April 1949. 

In December 1 949 Ansco proposed an- 
other type of perforation which they be- 
lieved might be superior to the Dubray- 
Howell. This is essentially the negative 
perforation but with fillets in the previ- 
ously sharp corners to provide additional 
strength. The Film Dimensions Com- 
mittee agreed to wait six to eight months 
while Ansco conducted their tests and to 
then review all the experimental evi- 
dence. This was done at a subsequent 
meeting in October 1 950. The compari- 
son of the Dubray-Howell and "modified 
negative" showed little difference as to 
camera steadiness but definite superiority 
with the latter in printing. The tests 
on projection life were not complete but 
in all cases the modified negative was 
never worse than the Dubray-Howell. 
(For a more complete history on the 
Ansco proposal see the W. G. Hill paper 
in the August 1951 Journal, p. 108.) 

The Film Dimensions Committee rec- 
ommends preliminary publication of 
the Dubray-Howell proposal at this time, 
under the belief that: (1) it is not advis- 
able to delay action until final proof is at 
hand as to the best type of perforation, 
and (2) the present wide use of the Du- 
bray-Howell perforation means that it is 
probably here to stay for some time. 
The proposal is labelled "an alternate 
standard" in view of the continued use- 
fulness of the present standards and the 
possibility of a fourth standard becoming 
the ultimate universal single standard. 



276 



September 1951 Journal of the SMPTE Vol.57 



Proposed American Standard 

Cutting and Perforating Dimensions for 

35-Mm Motion Picture Film -Alternate Standards 

for Either Positive or Negative Raw Stock 



PH 22.1 



P. 1 of 2 pp. 



a 
a 


a 
a 


a 

a x 
* 


a 


a 
a 


a 

-H 

i n 


za 

a 
1 4- 


a_ 
a_ 

^n 


Jct 





Dimensions 


Inches 


Millimeters 


A 


1.377 0.001 


34.980 0.025 


B 


0.1 870 0.0005 


4.750 0.01 3 


C 


0.1100 0.0004 


2.794 0.01 


D 


0.0730 0.0004 


1.85 0.01 


E 


0.079 0.002 


2.01 0.05 


G 


Not > 0.001 


Not > 0.025 


1 


0.999 0.002 


25.37 0.05 


L* 


18.700 0.015 


474.98 0.38 


R 


0.013 0.001 


0.330 0.025 



These dimensions and tolerances apply to the material immedi&tely after 
cutting and perforating. 

* This dimension represents the length of any 1 00 consecutive perfora- 
tion intervals. 



NOT APPROVED 



September 1951 Journal of the SMPTE Vol.57 



277 



Proposed American Standard 

Cutting and Perforating Dimensions for 

35-Mm Motion Picture Film -Alternate Standards 

for Either Positive or Negative Raw Stock 



PH 22.1 



P. 2 of 2 pp. 



Appendix 

The dimensions given in this standard represent the 
practice of film manufacturers in that the dimensions 
and tolerances are for film immediately after perfora- 
tion. The punches and dies themselves are made to 
tolerances considerably smaller than those given, but 
owing to the fact that film is a plastic material, the 
dimensions of the slit and perforated film never agree 
exactly with the dimensions of the punches and dies. 
Shrinkage of the film, due to change in moisture con- 
tent or loss of residual solvents, invariably results in 
a change in these dimensions during the life of the 
film. This change is generally uniform throughout the 
roll. 

The uniformity of perforation is one of the most im- 
portant of the variables affecting steadiness of pro- 
jection. 

Variations in pitch from roll to roll are of little sig- 
nificance compared to variations from one sprocket 
hole to the next. Actually, it is the maximum variation 



from one sprocket hole to the next within any small 
group that is important. 

Perforations of this size and shape were first de- 
scribed in the Journal of the SMPE in 1932 by Dubray 
and Howell. In 1937, a subcommittee report reviewed 
the work to date. The main interest in the perforation 
at that time was in its use as a universal perforation 
for both positive and negative film. The perforation 
has been adopted as a standard at this time largely 
because it has a projection life comparable to that of 
the perforation used for ordinary cine positive film 
(Z22.36-1947), and the same over-all dimensions as 
the perforations used in the negative film (Z22.34- 
1949). It should be particularly noted that although 
the present standard has the same over-all dimen- 
sions as the older cine negative perforation, position- 
ing pins or sprocket teeth made to fit this perforation 
exactly will injure the corners of the cine negative 
perforation. 



NOT APPROVED 



278 



September 1951 Journal of the SMPTE Vol. 57 



Engineering Activities 



PH22 

A meeting of ASA Sectional Committee 
PH22, chaired by J. A. Maurer, was held 
May 2, 1951. The Chairman noted that 
for the last several years the function of 
PH22 has been primarily one of formally 
validating proposed standards already 
thoroughly reviewed by several SMPTE 
Committees. However, the forthcoming 
meeting of the International Organiza- 
tion for Standardization (ISO) in the 
United States sometime during the 
summer of 1952 requires that PH22 play 
a more fundamental role. 

ISO's Technical Committee 36 on Cin- 
ematography (ISO/TC 36) was formed in 
1948 for the purpose of preparing world 
standards in the field of cinematography. 
The secretariat for this Committee is 
assigned to the ASA, which means, in 
effect, that PH22 is given the responsibility 
for technical developments leading to 
world standards in this field. However, 
outside of a limited exchange of corre- 
spondence, no formal action has been taken 
and no formal meeting of ISO/TC 36 has 
ever been held. 

It has been suggested that a first meeting 
of ISO/TC 36 should be held in the 
United States some time during the 
summer of 1952 probably in New York 
City. The technical responsibility for 
formulating an agenda for this meeting 
belongs to PH22, and since this agenda 
must be determined six months in advance 
of the meeting date, negotiations leading 
to its determination must be concluded by 
the end of this year. In order to get 
things started, Mr. Maurer advised that 
he, in cooperation with SMPTE Engineer- 
ing Vice-President F. T. Bowditch, had 
reviewed all current American Standards 
and recent proposed standards, and that 
these had been referred to the appropriate 
SMPTE Engineering Committees and to 
the Motion Picture Research Council 
with the request that a definite recom- 
mendation with respect to international 
standardization be submitted in each 
case, together with reasons for such 
recommendations. 

In the discussion the question was 
raised as to whether the agenda for this first 



meeting should include all possible standards 
or only the most important ones. It was 
finally agreed that the agenda should be 
confined to the most essential matters, 
leaving simply as "not proposed" those 
present standards considered either not 
suitable or not important. 

As a matter of procedure in defining the 
agenda, it was agreed that a formal letter 
ballot of the entire PH22 Committee is 
not required. When the SMPTE notifies 
the Chairman of PH22 that a group of 
standards has been considered suitable for 
consideration as world standards, he will 
send out a letter notifying the members 
of PH22 of this recommendation, giving 
a limited period of, say, two weeks during 
which any member may register any 
objections he may have. 

In addition to the discussion on ISO/TC 
36, a limited discussion took place on the 
procedure for review of foreign draft 
standards. The newly defined scope of 
PH22, was endorsed by the Committee 
as read. 



Optics 

The Optics Committee met on May 3, 
1951, under the Chairmanship of R. 
Kingslake. Two subjects were discussed 
at this meeting : (a) the Proposed Standard 
for Lens Aperture Calibration and (b) 
the general problem of standards for 8-mm, 
16-mm and 35-mm projection lenses. 

The lens aperture calibration proposal 
was discussed in detail and a new draft 
drawn up. (This proposal will appear 
in the October 1951 Journal.} 

The only current standard for projection 
lenses is the standard for the mount of a 
projection lens for 16-mm projectors 
using a 2.062-in. barrel, established by 
Committee Z52 during the war and re- 
printed in JAN-P-49. This lacks a few 
detailed specifications and will be redrawn 
by the Optics Committee. The Com- 
mittee agreed that similar specifications 
should be set up for home 8-mm and 16- 
mm projectors. Dr. Pestrecov and Mr. 
Maulbetsch were asked to draw up similar 
outline limitations for two sizes of 35-mm 



279 



projection lenses. These will then be 
sent to all projector and lens manufacturers 
for comment. 

Film Projection Practice 

This Committee held its first meeting under 
its new Chairman, M. D. O'Brien, on 
May 3, 1951. Past activity and inactivity 
were discussed and plans made for future 
action. Specific issues tackled were: 

1. Projection- Room Plans. This is to be 
reviewed and revised by a task group of 
three and prepared for Journal publication. 

2. Projection- Room Maintenance Instructions. 
The advisability of this project was ques- 
tioned and the Chairman is to give it 
further study. 

3. Lamp-Mounting Dimensions. The need 
for standardization was emphasized and a 
survey on existing equipment proposed. 
Mr. Davee accepted responsibility for the 
initial phase of this project. 

4. Review of Standards. Two Standards, 
PH22.28 and PH22.58, were studied as 
potential International Standards but 
rejected on the grounds that they required 
revision. Messrs. Schlanger and Todd 
agreed to draw up a new draft of PH22.28. 
The Committee did not wish to over- 
extend its initial activity and, therefore, 
relegated revision of PH22.58 for future 
action. Review of PH22.4 was on the 
agenda but was also tabled for future 
consideration. 



Films for Television Committee 

The emulsion position of 16-mm film 
(toward screen or lens) has been a vexing 
problem for some time and it was again 
reviewed at the May 2, 1951, meeting of 
this Committee. Dr. Garman, the Chair- 
man, stated that he had received a good 
deal of correspondence on this question 
and that it might be helpful if someone 
would abstract the gist of the comments. 
Mr. Schlafly offered to do this and Messrs. 
Dewhirst, Misener and Veal preferred 
additional information to help round out 
the picture. (A symposium on this topic 
is to be held at the Society's 70th Con- 
vention in Hollywood, October 15-18.) 

The new "Society Leader" was also 
discussed, the Subcommittee chaired by 
C. L. Townsend having asked the parent 
Committee for authorization to publish 
a status report. After making minor 
amendments, the Committee gave its 
approval for Journal publication. (The 
report was published in the May 1951 
Journal.} 

In addition, a new Subcommittee was 
formed, chaired by W. F. Little, dealing 
with the many problems relating to pic- 
torial quality of television films. The 
Subcommittee's scope will also include 
preparation of a glossary of terms peculiar 
to the subject material studied and a 
continued consideration of the 30-frame 
question. HK. 



Atlantic Coast Meeting on Animation 



At the March meeting of the Atlantic Coast 
Section of the SMPTE, Paul Terry of 
Terrytoons, New Rochelle, N.Y., showed a 
film describing the making of animated 
cartoons at his studios and then showed a 
couple of cartoons that had been featured 
in the "how-to." Mr. Terry himself sup- 
plied the narration. A brief history of ani- 
mation was presented with appropriate 
pictures and illustrations. 

Since the dawn of man, the artist has 
been intrigued with the idea of achieving 
not only a fine record of life and events in a 
work of art, but also actual records of 
scenes in motion. The photographer at- 
tained motion when the motion picture 



camera was perfected, but the draughts- 
man had the difficult handicap of attempt- 
ing to record a drawing so that it appeared 
to be an actual movement. 

The Stone Age genius who drew the 
Wild Boar of Altamira in Spain 20,000 years 
ago, suggested the motion of a running 
beast by drawing wiggly lines by its legs, 
exactly as the comic-strip artist renders it 
today. This represents, perhaps, the very 
first suggestion of animation. The Egyp- 
tian Goddess Isis was painted on each of 
110 columns on a temple in 1600 B.C. 
Each figure was in a progressively changed 
position so that a dashing charioteer passing 
by enjoyed an illustion of motion, with these 



280 



110 images merging into one dancing figure. 
The ancient Greeks and Chinese also did 
much the same thing on vases and scrolls. 

Others, including the versatile Leonardo 
da Vinci, rendered different positions of the 
human figure, in which several drawings 
were superimposed on one space, suggesting 
animation. 

Perhaps the first conscious attempt at 
comical drawings suggesting motion was by 
a German named Athanasius Kircher who 
devised the first magic lantern and did two 
drawings of a mouse crawling into a sleep- 
ing man's mouth. This was done in two 
projections of still drawings, like a comic 
strip, in 1640. 

In 1824, Peter Mark Roget discovered a 
vital principle of sight. He learned that 
the eye tends to retain an image it has just 
seen. If this were not so, motion pictures 
would be impossible. He built a spinning 
top that had a bird on one side and a cage 
on the other. When the top spun, the bird 
seemed to be in the cage. 

William Lincoln patented a device called 
the Zoetrope in 1867, and this marked the 
introduction of animated cartoons into this 
country. It consisted of a wide shallow 
cylinder, mounted on a stand. The cylin- 
der had a number of spaced slits near the 
tops and the drawings, made on a strip of 
paper about two and a half feet long, were 
inserted on the inside of the cylinder. As 
the cylinder revolved, one would look 
through the moving slits and there would 
be a sense of motion of the slightly different 
drawings on the strip. 

There were many pioneers who struggled, 
often in vain, to perfect better devices for 
animation. One even lost his sight as a 
result of such a striving, and the world is 
deeply indebted to these great persistent 
men. 

The common "flipper book" was intro- 
duced in 1 868. It was made up of a pad of 
drawings bound in book fashion along one 
edge. The book was held in one hand, 
along the bound edge, while the other hand 
flipped the pages. As they slipped from 
under the thumb, the drawings, all in se- 
quence, passed quickly before the eyes and 
gave the illusion of continuous motion 
the animated cartoon. 

The first experimental cartoon was crea- 
ted by a newspaper artist named James 



Stuart Blocton, encouraged by Thomas A. 
Edison. He made 3000 drawings of funny 
faces and jugglers and called it "Humorous 
Phases of Funny Faces." It was exhibited 
to the public, which found it hilarious fare 
in 1906. 

To Winsor McCay, another newspaper 
artist, goes credit for the animated cartoon 
in the form in which it appears today. 
In 1909, he made Gertie, the Dinosaur, the 
first complete story-depicting animated 
cartoon. In all, McCay made ten car- 
toons, and the work that went into each 
cartoon was staggering. He drew all the 
thousands of pictures complete with back- 
ground scenes in each. 

Paul Terry pays the greatest tribute to 
McCay, not only as the man who inspired 
him to start his own animated cartoon 
productions, but as the artist whose knowl- 
edge, ability and vision foresaw its tre- 
mendous possibilities. 

In 1915, Paul Terry, then a newspaper 
cartoonist, developed the first process for 
making one background for a scene and 
doing the animations on celluloid and 
superimposing them on the backgrounds, 
thus vastly reducing the labor. In that 
year, Mr. Terry patented the first double- 
exposure process. At present he turns out 
26 two-reel features a year at his New Ro- 
chelle plant. 

The development of both music and 
story ideas which go into Terrytoons was 
shown in color movies of Mr. Terry's 80- 
man staff at work. Music and sound-strip 
come first, even as in Tales of Hoffman, then 
story and pictures are tailored to fit. Rap- 
port exists between composers and writers, 
however, and the composers do the score 
with a certain story line in mind. If 
Mighty Mouse is to kiss his lady, the length 
of time is estimated before the composer sits 
down at the piano. A good many motions 
are rehearsed and clocked on a metronome 
in these precomposition conferences, and 
Mr. Terry assured his audience that even a 
bull being tossed out of an arena can be 
"seen" and timed by the conferees. This 
throwing of the bull, however, does not 
impede production. 

In addition to the above report, which 
was kindly checked by Mr. Terry, we have 
been able to get the following reference list 
from Ernest M. Pittaro. 



281 



A Reference List on Animation 

SMPE Journal Articles 

J. A. Nor ling, "Trick and process cinema- 
tography," Jour. SMPE, vol. 28, pp. 

136-157, Feb. 1937. 
J. E. Burks, "A third-dimensional effect in 

animated cartoons," Jour. SMPE, vol. 28, 

pp. 39-42, Jan. 1937. 
E. Theisen, "The history of the animated 

cartoon," Jour. SMPE, vol. 21, pp. 239- 

249, Sept. 1933. 
W. Garity, "The production of animated 

cartoons," Jour. SMPE, vol. 20, pp. 309- 

322, Apr. 1933. 

Magazine Articles 

J. Noble, "History of the animated film," 

Intern. Phot., vol. 21, Pt. I, pp. 13-16, 

Apr. 1949; Pt. II, pp. 13-16, May 1949. 
N. Taylor, "Animated movie making for 

the beginner," Home Movies, Aug. 1946. 
H. Black, "Lucite and Lantz came through 

for the Navy," Am. Cinemat., vol. 26, pp. 

372-373, 392, Nov. 1945. 
W. Bosco, "Harman unveils new animation 

unit," Am. Cinemat., vol. 26, pp. 190-191, 

June, 1945. 
A. Wolff, "Simple cartoons," Movie Makers, 

vol. 18, pp. 472, 492-493, Dec. 1943. 
C. Randall, "Animation for amateur de- 
fense films," Home Movies, vol. 9, pp. 185, 

206-207, May 1942. 
G. Fallberg, "Animated cartoon production 

today," Am. Cinemat., vol. 23: Pt. I, pp. 

151, 188-190, Apr. 1942; Pt. II, pp. 202- 

203, 232-237, May 1942; Pt. Ill, pp. 

250-251, 282-285 June 1942; Pt. IV, pp. 

300-303, 331-332, July 1942; Pt. V, pp. 

344-346, 380-382, Aug. 1942. 
M. Goldberger, "Making maps move," 

Movie Makers, vol. 11, pp. 479, 489-490, 

Nov. 1936. 
W. Lantz, "Synchronizing sound cartoons," 

Am. Cinemat., (Amateur Movie Section) 

vol. 16, pp. 76, 82-83, Feb. 1935. 
H. Angell, "Animation Advice," Movie 

Makers, vol. 8, pp. 152-153, 170, Apr. 

1933. 
W. Lantz, "Sound cartoons and 16-mm," 

Am. Cinemat., vol. 13, pp. 36-37, 41, July 

1932. 

Books 

Raymond Spottiswoode, Film and Its Tech- 
niques, University of California Press, Los 
Angeles, 1951, pp. 120-146. 



W. Foster, Animated Cartoons, Foster Art 
Service, Inc., Laguna Beach, Calif., 36 
pps. Very little text, all drawings and 
charts for those interested in the drawing 
phase of animated cartoons. This is an 
excellent treatment of modern animated 
cartoon technique. 

P. Blair, Advanced Animation, Foster Art 
Service, Inc., Laguna Beach, Calif. 
This again treats the drawing and car- 
tooning aspect of animation. It is an 
excellent reference and in constant use by 
professional animators in the industry 
but of interest to those looking for infor- 
mation about the drawing of animated 
cartoons, not their production from a 
technical standpoint. 

J. Battison, Movies for TV, Macmillan, New 
York, 1950. One chapter in which ani- 
mation comes in for a light lay treatment. 

H. Gipson, Films in Business and Industry, 
McGraw-Hill, New York, 1947, 291 pps- 
Several mentions and many reproduc- 
tions of various types of animation with 
chapter on animation. Well worth 
reading. 

A. Epstein, How to Draw Animated Cartoons^ 
Greenberg Publishers, 201 E. 57th St., 
New York, 1945, 64 pp. A superficial 
treatment of animation from the drawing 
standpoint. 

R. Field, The Art of Walt Disney, Macmillan, 
New York, 1942, 290 pps. Written from 
the lay viewpoint. Of interest from the 
drawing standpoint, containing many ex- 
cellent reproductions of Disney cartoons. 

N. Falk, How to Make Animated Cartoons, 
Foundation Books, New York, 1941, 79 
pps. A nontechnical treatise of interest 
to the layman. 

E. Lutz, The Motion Picture Cameraman, 
Scribners, New York, 1927, 248 pps. 
This book is outdated, but has a chapter 
with interesting information relative to 
animation. 

E. Lutz, Animated Cartoons, Scribners, New 
York, 1926, 261 pps. Although out- 
dated, this book contains some valuable 
information. 

If readers know of additional sources of infor- 
mation about animation, correspondence will be 
welcomed by Ernest M. Pittaro, 137-65 70th 
Ave., Flushing, N.Y. 



282 



International Commission on Illumination 



Among the organizations in which our 
Society maintains official representation is 
the United States National Committee of 
the International Commission on Illumi- 
nation. 

Present SMPTE representatives to the 
USNC whose terms continue until De- 
cember 31, 1952, are: Herbert Barnett, 
General Precision Laboratory; R. E. 
Farnham, General Electric Co. ; and H. 
E. White, Eastman Kodak Co. 

The ICI has these objectives: 

1. to provide an International forum 
for all matters relating to the science and 
art of illumination ; 

2. to promote by all appropriate means 
the study of such matters; 

3. to provide for the interchange of 
information between the different coun- 
tries ; and 

4. to agree upon and to publish inter- 
national recommendations. 

"While owing its chief allegiance to this 
country, the United States National Com- 
mittee desires to cooperate fully and 
cordially with the ICI and its other na- 
tional committees for the promotion of the 
science and art of illumination and for the 
establishment of cordial international rela- 
tions. It is important that those who act 
for the Committee keep these objectives 
fully in mind, and diplomatically extend 
friendly helping hands to other countries 
without permitting American ideals to be 
sacrificed or ignored." 

During Session XII of the ICI held in 
Stockholm, Sweden, June 26 to July 7, 
1951, Dr. Ward Harrison of the United 
States was elected president of the Com- 
mission for a term ending in 1955. 

C. A. Atherton of the United States, 
long a delegate to the ICI, was elected 
Honorary Secretary. A paper prepared by 
Ralph Evans (Eastman Kodak Co.) was 
presented by Dr. Dean B. Judd of the 
National Bureau of Standards, because 
Ralph was unable to attend. 

Numerous items on the agenda of Session 
XII include such matters as definitions of 
fundamental terms used in the field of 
illumination and photometry, and stand- 
ards of luminous intensity and luminous 
flux. Scotopic luminosity functions for 



young eyes were discussed and relative 
luminosity values to be used in determining 
threshold response were set down at length. 
In addition, attention was given to such 
practical matters as highway lighting and 
automobile headlights. Of particular in- 
terest to Society members were the recom- 
mendations presented on the subject of 
theater screen lighting and television. 
These are quoted in their entirety : 

Committee 62d, Screen Lighting 
in Cinemas 

"7. Screen brightness. When showing 35- 
mm film it is recommended that the 
brightness measured in the middle of the 
screen shall be 35 (+15-10) nit. Whilst 
the measurements are being taken, the 
projector is to be running without film. 
The arc lamp current desired shall be 
accurately set, and the arc lamp shall be 
adjusted to give maximum lighting in the 
middle of the screen. In the middle of 
the short side of the screen the brightness 
must not be below 75% of the value in 
the middle of the screen. 

"2. It is further recommended that the 
Secretariat Committee shall study the 
question of desirable brightness values for 
screens less than 3 m or more than 8 m 
wide. 

"3. Stray light. The Cinema Lighting 
Committee draws attention to the French 
experiments indicating that the screen 
brightness, due to stray light (measured 
with the projector running) should not 
exceed 5% of the value obtained with the 
projector operating without film in it, and 
recommends that National Committees 
should make similar experiments. 

"4. Brightness of Surround. It is recom- 
mended that each country report at the 
next meeting, information of brightness 
screen surround, preferably including 
screen brightness values as well." 

Committee 63, Television 

"7. It is desirable that each interested 
country, prior to the next session, should 
propose a report covering lighting develop- 
ments in the field of black-and-white 
television (lighting of the studios and for 
reception). 



283 



"2. It is suggested that a special sub- 
committee be appointed to deal with color 
television. 

"3. It is desirable to collect information 
dealing with the ambient lighting used 
when viewing. 

"4. It is desirable to propose in collabo- 
ration with the transmission authorities, 
instructions for the use of televiewers, 



which will enable them to adjust their 
receivers to give the best reception. 

"5. It is desirable that a thorough 
study should be made with the object of 
improving the quality of films used in 
television. 

"6. It is desirable that a study of visual 
fatigue due to viewing be made in each 
country in collaboration with the appro- 
priate medical body." 



New Members 



The following members have been added to the Society's rolls since those last published. 
The designations of grades are the same as those used in the 1950 MEMBERSHIP DIRECTORY, 



Honorary (H) 



Fellow (F) 



Active (M) 



Associate (A) 



Student (S) 



Apitsch, John W., Sound Engineer, 
Twentieth Century-Fox Film Corp. 
Mail: 10367 Cheviot Dr., Los Angeles 
64, Calif. (A) 

Bury, John L., Jr., University of Holly- 
wood. Mail: 226 Argonne Ave., Long 
Beach 3, Calif. (S) 

Demoreuille, Pierre, President, The Car- 
bone Corp. Mail: 10 Bowers Rd., 
Caldwell, N. J. (M) 

Gramaglia, Albert A., Sound Mixer, RCA 
Sound Recording Div. Mail: 685 E. 
237 St., New York 66, N.Y. (A) 

Haburton, Ralph, Chief, Processing 
Branch, Motion Picture Section, U.S. 
Air Force, Wright-Patterson Air Force 
Base. Mail: 1335 Oakdale Ave., Day- 
ton 10, Ohio. (M) 

Herald, Robert L., 1306 N. Pennsylvania 
St., Indianapolis, Ind. (A) 

Hurd, Yorick G., Physicist, Twentieth 
Century-Fox Film Corp. Mail: 228- 
35 Men tone Ave., Rosedale 10, L.I., 
N.Y. (M) 

Kammerer, Guenter, Technician. Mail: 
c/o The Vines, 1208 Drummond St., 
Montreal, P.Q., Canada. (A) 

Knutson, N. Theodore, New Product 
Designer, Bell & Howell Co. Mail: 
5230 Oakdale Ave., Chicago 41 , 111. (A) 

Koeber, Henry J., Jr., Design Engineer, 
Bell & Howell Co. Mail: 4144 N! 
Olcott, Chicago 34, 111. (A) 

Lakemacher, Elmer E., Machine Design 
Engineer, Bell & Howell Co. Mail: 
3828 N. Kenneth Ave., Chicago 41, 111. 

(A) 

Lewis, David L., Production, 16-Mm Mo- 
tion Pictures, Northrop Aircraft Co. 
Mail: 361 9 Marcia Dr., Los Angeles 26, 
Calif. (A) 



Lucas, Robert James, Chief Technician, 

Metro-Goldwyn-Mayer. Mail: 7 Orient 

St., Gladesville, Sydney, N.S.W., Aus- 
tralia. (A) 
Mentz, Charles H., Television Engineer, 

KPIX. Mail: 416 Serrano Dr., San 

Francisco, Calif. (A) 
Miyamoto, Toshio, Manager, Fukujiro 

Fukano. Mail: 876 Shimokomatsu- 

Machi, Katsushika-Ku, Tokyo, Japan. 

(M) 
Mylander, Karl F., Ohio State University. 

Mail: 331 East Water St., Oak Harbor, 

Ohio. (S) 
Nupnau, Arthur, Junior Design Engineer, 

Bell & Howell Co. Mail: 3916 N. 

Sawyer Ave., Chicago 18, 111. (A) 
Oliveri, Paul, Motion Picture Laboratory 

Technician, U.S. Army Signal Corp. 

Mail: 114-1 71 28th St., South Ozone 

Park, N.Y. (A) 
Poulson, William R., TV Films, 16-Mm 

Laboratory. Mail: 5044 Walmar Ave., 

La Canada, Calif. (A) 
Quateman, Joseph, Bell & Howell Co. 

Mail: 2533 Jackson, Evanston, 111. 

(A) 
Roos, Dirk J., Manager, Sound Division, 

Radio Specialties Co. Mail: 34480 

Capitol Dr., Plymouth, Mich. (A) 
Schwartzberg, Henri, Motion Picture 

Film Buyer, American Theatres Corp. 

Mail: 72 Beaconsfield Rd., Brookline 

46, Mass. (A) 

Seward, Edward, Free-lance Motion Pic- 
ture Director. Mail: 331272 St., 

Jackson Heights, L.I., N.Y. (M) 
Shimek, John A., Production Engineer, 

Bell & Howell Co., 1700 McCormick 

Rd., Chicago 45, 111. (A) 



284 



Strung, William C., Specialist, 16-Mm Film 
Reports, North American Aviation, Inc. 
Mail: 4454 Lakewood Blvd., Long 
Beach 8, Calif. (A) 

Thornwald, Everett D., Design Engineer, 
Bell & Howell Co. Mail: 1348Vs 
Estes Ave., Chicago 26, 111. (A) 

Vinton, William H., Research Manager, 
Du Pont Photo Products. Mail: Du 
Pont Club, Parlin, NJ. (M) 

Wagner, Karl L., Independent Producer. 
Mail: 501 C.C. Bk. Bldg., Des Moines 
9, Iowa. (M) 

Walker, Edwin M., Motion Picture Labo- 
ratory Technician, U.S. Air Force, 
Wright-Patterson Air Force Base. Mail: 
931 Crestmore Ave., Dayton, Ohio. 
(M) 

Weber, John P., Jr., Electronics Design 
Engineer, Bell & Howell Co. Mail: 
6440 N. Albany, Chicago 45, 111. (M) 

West, John H., In charge, Film Renovat- 
ing and Treating Laboratory, Rapid 
Film Technique. Mail: 3525 77th 
St., Jackson Heights, L.I., N.Y. (M) 



CHANGES IN GRADE 

Choudhury, Siraj-ul-Islam, Free-lance 
Artist, Motion Picture Production, Dept. 
of State and News of the Day. Mail: 
235 Eldridge St., New York 2, N.Y. 
(S) to (A) 

Townsend, Charles L., TV Technical 
Film Director, National Broadcasting 
Co. Mail: 49 Hillcrest Dr., DuMont, 
NJ. (A) to (M) 

Vosburgh, Richard V., TV Film Editor 
and Cameraman, Paramount TV Pro- 
ductions. Mail: 5800 Green Oak Dr., 
Hollywood 28, Calif. (S) to (A) 



DECEASED 

Ball, J. Arthur, Consulting Engineer, 
Color Photography. Mail: 12720 High- 
wood St., Los Angeles 49, Calif. (F) 

Winter, Ernest A., Service Inspector, 
Western Electric Co., Ltd. Mail: 14 
Hawkeshead St., Southport, Lancaster, 
England. (A) 



Obituary 



J. Arthur Ball died in Los Angeles on 
August 27 at the age of 57. In recent 
years he was actively engaged as a color 
consultant, dividing his time between 
Los Angeles and New York. 

He was an alumnus of Massachusetts 
Institute of Technology and was long 
associated with Technicolor, as an execu- 
tive of Technicolor, Inc., and with its 
subsidiary, Technicolor Motion Picture 
Corp. which manufactures the color films. 
He was Technical Director for Technicolor 
when the firm made Becky Sharp, which 
was a forerunner of a long line of color 
motion pictures. In 1938, Mr. Ball was 
given an Oscar by the Academy of Motion 
Picture Arts and Sciences for his con- 



tributions to color motion pictures. Many 
of his patents in the field of color photog- 
raphy were assigned to Technicolor for 
whom he built a camera reported to have 
cost $15,000 and five months time to 
make. 

As a consultant he had served the Photo 
Products Dept. of E. I. du Pont de Nemours 
& Co. since early 1946. During this time 
he had assisted in the development of 
Du Font's recently introduced motion 
picture color positive film and on other 
color motion picture products. He was 
also recently a color consultant for the 
Springdale Laboratories of Time, Inc., at 
Stamford, Conn., and for Walt Disney 
Productions. 



Motion pictures in color depend on the engineers' knowledge of the "Principles of Color 
Sensitometry." A 72-page article bearing that title and prepared by the Color Sensitom- 
etry Committee appeared in the Journal for June 1950. Attractive reprint copies may 
be purchased for $1.00. 



SMPTE Officers and Committees: The roster of Society Officers and the 
Committee Chairmen and Members were published in the April Journal. 



285 



Current Literature 



The Editors present for convenient reference a list of articles dealing with subjects cognate 
to motion picture engineering published in a number of selected journals. Photostatic 
or microfilm copies of articles in magazines that are available may be obtained from The 
Library of Congress, Washington, D.G., or from the New York Public Library, New 
York, N.Y., at prevailing rates. 



American Cinematographer 

vol. 32, Apr. 1951 
Under Water With the Aquaflex (p. 132) 

7*. Gabbani 
Editing Magnetic Sound (p. 137) L. L. 

Ryder 
Ten Basic Factors of TV Film Production 

(p. 138) A. L. Marble 

vol. 32, May 1951 

The Westrex Magnetic Film Recording 
Systems (p. 182) R. Lawton 

Hollywood Knowhow in TV Film Pro- 
duction (p. 184) L. Alien 

In the Best Professional Manner (p. 186) 
W. Strenge 

vol. 32, June 1951 

The Kinevox Synchronous Magnetic Film 
Recorder (p. 224) R. Lawton 

Station-Production of TV Motion Pictures 
(p. 226) D. L. Conway 

vol. 32, July 1951 
Evolution of the Viewfinder Ground Glass 

(p. 262) J. V. Noble 

The Stancil-Hoffman Synchronous Mag- 
netic Film Recorder (p. 264) R. Lawton 
Economical TV Filming (p. 268) J. H. 
Battison 

Audio Engineering 

vol. 35, Aug. 1951 
Efficiency of Direct-Radiator Loudspeakers 

(p. 13) V. Salmon 
A New Approach to Loudspeaker Damping 

(p. 20) W. Clements 

British Kinematography 

vol. 17, Dec. 1950 

Practical Applications of Magnetic Re- 
Recording Tape and Film, Pt. I, 
Historical Aspects (p. 182) K. G. Gould 
Engineering Aspects of Film Production 
(p. 196) /?. Howard Cricks 

vol. 18, Jan. 1951 
Motion Picture Presentation (p. 4) S. B. 

Swingler and R. R. E. Pulman 
Technical Objectives in Pre-Planning 

Production (p. 18) K. E. Harris 

vol. 18, Feb. 1951 

Economic Aspects of Studio Lighting, Pt. 
I, Series-Parallel Wiring of Arcs (p. 44) 
C. W. Hilly er 



Back Projection in the Kinema (p. 56) 
/. L. Stableford 

vol. 19, July 1951 

Presidential Address (The Motion Picture 
Industry) (p. 13) L. Knopp 

The Magnetic Recording and Reproduc- 
ing Equipment for the Telekinema (p. 
19) G. F. Button 

Electronics 

vol. 24, May 1951 

Constructing the Tricolor Picture Tube 
(p. 86) 

vol. 24, July 1951 
Continuous Film Scanner for TV (p. 114) 

vol. 24, Aug. 1951 
Plans for Compatible Color Television 

(p. 90) 
Picture Generator for Color Television 

(p. 116) R. P. Burr, W. R. Stone and R. 

O. Noyer 

General Electric Review 

vol. 54, June 1951 

Spectrum Utilization in Color Television 
(p. 18) R. B. Dome 

vol. 54, July 1951 

Over-Age Lamps May Mar Television 
Reception (p. 42) J. H. Campbell and 
H. E. Schultz 

Ideal Kinema 

vol. 17, May 17, 1951 
Projection Equipment in the Telekinema 

(p. 7) R. H. Cricks 
Televised Pictures on Large Screen (p. 9) 

International Projectionist 

vol. 26, Apr. 1951 

Honeycomb-Condenser Lamp Optics (p. 
5) A. R. Schultze 

Evaluating the Honeycomb-Condenser 
Lamp (p. 6) R. A. Mitchell . 

Comparative Data Anent Nitrate Safety 
Film (p. 13) 

Theater Television via the RCA PT-100 
Equipment, Pt. V, Projectionist Operat- 
ing Procedure (p. 18) RCA Service Co., 
Technical Products Division 

vol. 26, May 1951 
The Magic of Color (p. 13) R. A. Mitchell 



286 



Theater Television Via the RCA PT-100 Radio & Television News 

Equipment, Pt. VI, Interpretation of vol. 46, July 1951 

Image Characteristics (p. 18) Practical Sound Engineering, Pt. V, A 

. _ , T 10C1 Brief History of Early Experiments in 

vol. 26, June 1951 Reproducing Sound as Compared With 

Lens-Correction : What it Means (p. 5) Modern Systems (p. 60) H. M. Tremaine 

E. Murray The p ro blem of Recording TV Frequencies 

GPL's New 16-Mm Sprocket Intermittent / 16) 7 D Goodell 

(P- 20) vo l. 46> Aug. 1951 

vol. 26, July 1951 TV Pictures in Color (p. 38) N. Chalfin 
The Magic of Color (p. 5) R. A. Mitchell 



vol. 10, June 1951 

Television Films Adapt TV Techniques 
vol. 183, Pt. 2 (Better Theatres), (p. 38) /. H. Battison 

June 2, 1951 vol. 10, July 1951 

Changing to Faster Lenses Can Increase Latest Color Television Developments (p. 
Screen Light (p. 31) G. Gagliardi 28) 

Your Journals bound make a valuable permanent reference. Six issues constitute a 
Volume and should be bound with the special contents page (supplied beginning with 
Vol. 56) and index furnished with each June and December issue. For details of binding 
see page 702 of the June 1951 Journal. 

Journal indexes covering the thirty-four years from 1916 through 1950 may be purchased 
from Society Headquarters. 

1916-1930 $1.25 1930-1935 $1.25 1936-1945 $2.00 1946-1950 $1.50 

American Standards form the technical foundation for motion pictures around the 
world. All current standards were listed by subject and by number in the Journal Index 
1946-1950. Reprint copies of this list, which includes all previous Journal references to 
each standard, are available from Society Headquarters without charge. 

Complete sets of all sixty current standards in a heavy three-post binder with the index 
are $13.50, plus 3% sales tax for purchases within New York City, and are available from 
Society Headquarters. Single copies of any particular standard must be ordered from 
the American Standards Association, 70 East 45th St., New York 17, N.Y. 

Test films are the customary tool for checking picture and sound performance in theaters, 
service shops, in factories and in television stations. Twenty-seven different test films 
in 16- and 35-mm sizes are produced by the Society and the Motion Picture Research 
Council. Write to Society Headquarters for a free catalog. 

Meetings of Other Societies 

Theatre Equipment and Supply Manufacturers' Association (in conjunction with Theatre 

Equipment Dealers), Oct. 11-13, Ambassador Hotel, Los Angeles, Calif. 
National Electronics Conference, Seventh Annual Conference, Oct. 22-24, Edgewater 
Beach Hotel, Chicago. The conference is sponsored by the American Institute of 
Electrical Engineers, Institute of Radio Engineers, Illinois Institute of Technology, 
Northwestern University and the University of Illinois, with participation by the 
University of Wisconsin and the Society of Motion Picture and Television Engineers. 
The American Institute of Physics is holding a twentieth anniversary meeting in Chicago 
on October 23-27. Its member societies will hold meetings at that time as follows: 
Acoustical Society of America, Oct. 23-25 
Optical Society of America, Oct. 23-25 
Society of Rheology, Oct. 24-26 
American Physical Society, Oct. 25-27 
American Association of Physics Teachers, Oct. 2527 

287 



New Products 



Further information about these items can be obtained from the addresses given. As in 
the case of technical papers, the Society is not responsible for manufacturers' statements, 
and publication of news items does not constitute an endorsement. 

use for curve plotting in scientific, mathe- 
matical, engineering or statistical analysis. 
There are two forms: No. 1235 has one 
arctangent scale and one linear scale; 
No. 1236 (a portion of which is illustrated 



Dylewski ARKTAN is arctangent co- 
ordinate graph paper available as 8| X 
11 in. tracing paper at $1.00 per package 
of 20 sheets from Orbit Electric Co., 
2710 N. Menard Ave., Chicago 39. 
Available at no charge are samples of the 
paper and a bulletin describing the paper's 



below) has double arctangent coordinates. 































































































































































































































































































































































































































































































































































150 




























































175- 




















































































































































































250- 












































































































































































































































































































500 



























































































































































































































































































































































































































































































































































































































i < 


H 


r\ o 


Is 

1 - 


4 


:! 


> c 

: 


11 


Li 


' i 


i < 


?< 


IS 


^ I 

\ K 


I S 

N C\ 


^ L 



N C 

IS 


> U 
> 


" S 


Lf 

- <\ 


" 


; jj 


:c 
M 


> \J 
^ C\ 


-v 
I 
C 


1 

r 

> 


~\ C 

J L 


> J 

^ ^ 


: | 



Erratum 



The Utili scope, the closed-circuit television system that was described in the July 1951 
Journal, is made by the Diamond Power Specialty Corp. in Lancaster, Ohio, not in Lan- 
caster, Pennsylvania, as erroneously cited in the Journal. This is the industrial television 
system that has been receiving a good deal of attention in the press because of the wide 
variety of applications reported, including use in motion picture production. 



288 



Electrical and Photographic Compensation 
in Television Film Reproduction 

By P. J. HERBST, R. O. DREW and S. W. JOHNSON 



JL. HE REPRODUCTION of filmed material 
over the television system seldom ap- 
proaches the quality of direct projection. 
The degradation in quality is usually 
apparent as loss of detail, compression 
in both the highlights and the shadows, 
increased fluctuation noise and the 
introduction of spurious signals in the 
form of shading, edge flare, spots and 
halo. Loss of detail and distortion of 
the contrast rendition can be reduced 
by the employment of electrical com- 
pensation. Such methods have been 
employed with varying degrees of success. 
The extent to which they can be used 
is limited by the aggravation of noise 
and spurious signals. Conventional 
photographic processes do not permit 
an increase in detail to be achieved while 
attempts to minimize the compression 
of the highlights and shadows by re- 
ducing the range of the positive trans- 
parency to be televised are accompanied 
by loss of resolution due to the lowered 
contrast in the fine detail. 

Aperture Loss 

The characteristics of the television 
system have been subjected to a compre- 
hensive analysis by O. H. Schade. 1 " 4 
In this analysis, the loss in resolution is 



Presented on May 1, 1951, at the Society's 
Convention in New York, by P. J. Herbst, 
R. O. Drew and S. W. Johnson, Engineer- 
ing Products Dept., RCA Victor Div., 
Camden 2, N. J. 



considered as aperture loss and an 
effective scanning aperture is established 
for each part of the system, including 
both the electrical and the photographic 
elements. This provides a means of 
comparing the resolving power of such 
diversified factors as spot size, frequency 
response, bandwidth, lens sharpness 
and emulsion resolution. 

The aperture loss in a television 
system is basically the same effect which 
occurs in the optical recording of sound 
on film with a slit of finite width. This 
effect has been thoroughly discussed by 
E. D. Cook* (in 1930). The effect may 
be illustrated by the simple case of a 
uniform rectangular aperture traveling 
across an area which consists of alternate 
black and white lines of equal width. 
The distortion and loss introduced by 
the finite dimensions of the aperture are 
shown in Fig. 1. 

The relation of the rectangular aper- 
ture to lines of several widths is shown 
at (a) in this figure. The fraction of 
the aperture area exposed to the white 
lines as the aperture progresses across 
the image is shown at (b). In order 
to provide a better concept of the 
subjective effect, the light flux through 
the aperture as it passes across lines 
having a 10:1 contrast ratio is shown 
at (c). It will be seen that all detail 
is somewhat degraded by a subjective 
widening of the white lines due to the 
distortion of the transition edges, and 



October 1951 Journal of the SMPTE Vol. 57 



289 



W-u/- W-SW 



C> RELATIVE DIMENSIONS OF APERTURE $ LINE STRUCTURE 



/\ / 
'_ W1_V7_V-V vv 



<b> FRACTION OF APERTURE NOT OCCLUDED 

L 2 y / \ A A ~7 

\ / \ AA/ro^: 




CO RELATIVE FLUX FOR CONTRAST RATIO OF IO I IN LINE 
STRUCTURE 



Fig. 1. Aperture flux (rec- 
tangular aperture). 



RElL/fTlVL LINE NUMBER = 



WIDTH OT APERTURE. 



WIDTH OF LINE. 



a 2 




RELATIVE. LINE NUMBER 



Fig. 2. Effective aperture 

response for square 

aperture. 



(a) High quality experimental 
flying spot scanner (limiting 
resolution 2500 lines) 

(b) Best iconoscope perform- 
ance (limiting resolution 
1200 lines) 

(c) Image orthicon (5655) and 
2-in. vidicon (limiting resolu- 
tion 800 lines) 

(d) Lowest iconoscope per- 
formance and 1-in. vidicon 
(limiting resolution 600 lines) 

Fig. 3. Effective aperture response of television pickup tubes. 




290 



October 1951 Journal of the SMPTE Vol.57 



that the peak-to-peak ratio drops rapidly 
when the width of the lines becomes less 
than the width of the scanning aperture, 
reaching zero when the width of the 
lines is one-half that of the aperture. 
The relative detail contrast may be 
obtained by integrating the waves 
shown at (b) over a half-cycle. Since 
the eye, when viewing fine detail, 
integrates a portion of the transition in 
obtaining the sensation of maximum and 
minimum brightness, this method pro- 
vides a measure of the apparent reduction 
in the ratio of the contrast between these 
two levels. The observed effect is the 
same as that produced when viewing 
lines of the original width but of lesser 
contrast. This is the equivalent square- 
wave response and determines the loss 
of detail in the system. (See Ref. 2, 
p. 250.) 

Figure 2 shows the calculated aperture 
response for a rectangular aperture. 
The gradual loss in effective resolution 
is apparent in this figure. 

In the television system, the effective 
apertures are essentially circular in 
shape and are not uniform in cross 
section. This, however, does not affect 
the application of this concept although 
the shape of the transition from black 
to white changes. The effective aper- 
ture response for several types of tele- 
vision pickup tubes is shown in Fig. 3. 
These curves do not include the losses 
of the camera lens or other parts of the 
television system. They represent the 
range of characteristics in pickup devices 
which may find application in televising 
motion picture film. A comprehensive 
discussion of aperture flux response 
factors is given by Schade. 2 

When several effective apertures are 
successively introduced into the system 
each contributes to degradation in detail. 
The method of computing the effective 
overall aperture for a number of aper- 
tures in cascade has been treated by 
Cawein. 6 This method is quite accurate 
for linear regions of the aperture re- 
sponse characteristics and states that 



the square of the effective aperture 
width of a number of cascaded apertures 
is equal to the sum of the squares of the 
individual aperture widths. Schade 2 
applies the same process but performs 
the calculation in terms of the line 
number at which a given aperture re- 
sponse is obtained. In this case the 
square of the reciprocal of the line num- 
ber of the system is equal to the sum of 
the squares of the reciprocals of the line 
numbers of the separate apertures pro- 
ducing the same relative response. 
This method has been employed to 
compute the effective aperture response 
of the system when televising 35-mm 
and 16-mm film. Figure 4 shows the 
calculated overall response including the 
losses introduced by the optical elements, 
the photographic process, a high-quality 
monitor and the television pickup tube. 
In this case a limiting resolution of 800 
lines was assumed for the pickup device 
as representative of the performance 
realizable in current operations. The 
equivalent response of direct projected 
film is plotted to the same scale for 
comparison. In this figure the line 
number represents television lines, i.e., 
both black and white lines are counted. 

Electrical Aperture Compensation 

It is apparent that fine detail in the 
television system corresponds to high 
frequencies in the video signal. The 
aperture loss is therefore equivalent 
to a reduction in the amplitude response 
as the frequency increases. In sound 
reproduction such losses are frequently 
corrected by employing electrical net- 
works which emphasize the higher 
frequencies and it appears possible to 
employ similar techniques in television 
equipment. Thus, "high-peaking" cir- 
cuits are used to accentuate the higher 
video frequencies in both transmitting 
and receiving apparatus. Since this 
does not affect the separation between 
scanning lines, it is effective only in the 
horizontal direction and does not afford 
an increase in vertical detail. 



Herbst, Drew and Johnson: Electrical and Photographic Compensation 291 



1.0 



6 



a 



RELGTWC- Bt 
' 



V> 



V 








35 MM, A5 



35 MM DICECT PROJECTION 



Ife MM, 



it, MM 



IOO 



200 300 

LIME- NUMBER 



400 



500 



tOO 



Fig. 4. Effective aperture response of television film (no 

compensation); limiting resolution of 800 lines assumed for 

pickup tubes; includes optical and photographic losses. 



1.0 



.5 



4 





\ 



\ 




\ 



\ 



35 MM, AS TEIL^VISELD 
35 MM DIRECT P4.OJELCTIC 




TEL.E.VISE.D 
I6MM DRECT PBOTE.CTION 



too 



2.00 000 400 

LINE NUMBE.K 



500 600 



Fig. 5. Effective aperture response of television film (after compensation); limiting 
resolution of 800 lines assumed for pickup tubes; includes optical and photographic 

losses. 



292 



October 1951 Journal of the SMPTE Vol. 57 



In a system of finite bandwidth such 
circuits produce transients or overshoots 
which appear in the image as white 
edges following black areas and vice 
versa. The effect is equivalent to the 
edge effects produced by some photo- 
graphic processes. In the television 
system both the phase and the amplitude 
characteristics of the compensating cir- 
cuit must be adjusted in order to obtain 
optimum compensation. When over- 
compensation is introduced into the 
system the transient effect produces an 
unnatural "relief" appearance which is 
highly objectionable. The optimum 
compensation which can be applied is 
determined by subjective effects and a 
complete evaluation remains to be 
accomplished. The effective aperture 
response of the television film process 
when the line number for a given re- 
sponse is increased by \/2 is shown in 
Fig. 5. It will be noted that if this 
aperture correction could be employed 
the detail in televised film would exceed 
the detail obtained in direct projection. 
Unfortunately, the extent to which such 
compensation can be applied is limited 
by the extent to which the noise in the 
picture is increased. 

System Noise 

Noise in the signal from various pickup 
devices is of three types. In devices 
which do not employ electron multipliers 
the noise originates in the grid circuit 
of the first amplifying stage and is 
therefore independent of the amplitude 
of the video signal. The energy distri- 
bution over the video spectrum is not 
uniform but increases with frequency. 
Although this high-frequency noise is 
less perceptible by the eye, the applica- 
tion of electrical aperture compensation 
tends to greater accentuation of this 
type of noise. The iconoscope and the 
vidicon are both devices of this type. 

The noise in the signal from image 
orthicons originates in the random 
fluctuations of the scanning beam. 
Since the signal is derived from a small 



modulation of this beam, the noise is 
independent of signal amplitude. It 
is uniformly distributed over the video 
spectrum and might therefore be con- 
sidered as permitting more aperture 
compensation to be employed than in 
the case of amplifier limited devices. 
However, it has been observed that the 
disturbance becomes more objectionable 
as the frequency decreases and that the 
compensation required to compensate 
properly for aperture response usually 
extends into this region. The exact 
weight to be assigned to the subjective 
effect produced by different types of 
noise has not as yet been agreed upon. 
In practice the difference, as it applies to 
the extent to which correction can be em- 
ployed, has been found negligible. 

The flying spot scanner also produces 
noise which is uniform over the video 
spectrum. In this case, however, the 
noise originates from random emission of 
photoelectrons rather than from fluctua- 
tions in a comparatively large beam cur- 
rent. The noise amplitude is therefore 
proportional to the square root of the 
signal current. The extent to which 
aperture correction can be employed is 
limited by the same considerations as 
apply in the case of the image orthicon. 

The actual signal-to-noise ratio will 
vary with the type of tube employed, 
the excellence of the particular unit and 
the conditions under which it is 
operated. Various measurements of 
camera-tube noise have been reported 
in theliterature. 3 (P- 524 )> 7 The subjective 
difference between "peaked" and "flat" 
noise prevents a precise comparison 
between tube types. However, quali- 
tative differences in the degree to which 
corrective techniques may be applied 
can be obtained by employing these 
published figures as a basis. A fair 
average of the signal-to-noise in the 
maximum highlight signal appears to 
be 100:1 for the iconoscope, the vidicon 
and the flying spot scanner. This ap- 
proximation is therefore employed in 
the further comparison of compensation 



Herbst, Drew and Johnson: Electrical and Photographic Compensation 293 



JANES 



TOW -RCA REVIEW 
3 SEPT. 1950 7 




MALF-PO /VEt 
LAW VlOlCOt 



f 



LINEAR 01 VICE 



r 9CANNEB 

:ON) 



2 4 8 10 *O 

ILLUMINATION (ARBITRARY UNITS) 

Fig. 6. Representative transfer characteristics of various types of television pickup 

devices. 



as applied to these devices. The noise 
level of the present types of image orthi- 
cons is somewhat higher, especially when 
the tube is operated below the "knee" 
of its transfer characteristic. For ex- 
ample, the Type 5655 signal-to-noise 
ratio can be expected to lie between 
35 and 50 to 1. Experimental image 
orthicons have been built in which 
signal-to-noise ratios exceeding 100:1 
have been measured. 

Transfer Characteristics of 
Television Pickup Tubes 

Compression in both highlights and 
shadows in the transmission of film 
material over the television system is 
due to nonlinearity of the transfer 
characteristics of the camera tubes and 
the monitors and to the limited range 
which can be accommodated by the 
system. The transfer characteristics of 
several types of pickup devices are 
plotted in Fig. 6. The characteristic 
given for the iconoscope is representative 
of the general shape of the response 



curve but is subject in practice to wide 
departures with the average lighting and 
the distribution of illumination. The 
characteristic shown for the image 
orthicon is likewise merely representa- 
tive since, in practice, the actual charac- 
teristic will depend upon the extent to 
which the highlights extend beyond the 
knee of the curve. The dynamic light- 
transfer characteristics of image orthicons 
has been treated by Janes and Rotow 8 
and found to vary considerably with 
background illumination. The curve 
shown represents a static characteristic 
and seems to indicate that no contrast 
will be obtained in the highlights. 
However, the discharge of the target 
areas adjacent to highlights reduces the 
potential of these areas and provides 
the differential signal representative of 
detail. When the highlights are per- 
mitted to exceed the knee of the transfer 
characteristic by an appreciable amount, 
the redistribution effect produces ob- 
jectionable halo, white objects being 
surrounded by black areas and detail 



294 



October 1951 Journal of the SMPTE Vol. 57 



in light objects being almost entirely 
lacking. The present types of image 
orthicons are quite limited in the light 
range which they can successfully ac- 
commodate. A range of 30:1 appears 
to represent a practical operating limit. 
Under studio conditions, flat lighting and 
fill lights can be employed to realize 
this restricted range. The contrast 
range in most motion picture positives 
processed for direct projection is con- 
siderably in excess of the image orthicon 
capabilities. Moreover, under practical 
operating conditions the attention re- 
quired to obtain optimum results is an 
objection. For these reasons the use of 
image orthicons of the currently available 
types for film pickup does not appear 
to be highly attractive at this time. 
Consideration will therefore be confined 
to the characteristics provided by the 
iconoscope, the vidicon and the flying 
spot scanner. 

The transfer characteristic of the 
flying spot scanner is linear, i.e., it has 
a slope of unity when plotted on logarith- 
mic coordinates. The present vidicons 
employed in industrial devices also have 
a linear transfer characteristic. A recent 
research being conducted at the RCA 
Laboratories under the direction of Dr. 
A. Rose makes the ultimate realization 
of a half-power law for the vidicon 
appear hopeful. 

Contrast Rendition Over the 
Television System 

In photography the contrast rendition 
in the final print is determined by the 
combined sensitometric characteristics 
of both negative and positive, by the 
maximum contrast which can be 
achieved, and by the flare light intro- 
duced by the printing process. The 
video signal from the television pickup 
device is modified in a similar manner 
by the characteristics of the video ampli- 
fier and the viewing monitor. The 
contribution of these various devices to 
the overall transfer characteristic is 
illustrated in Fig. 7. 



In this illustration it will be noted 
that the viewing kinescope has a charac- 
teristic which follows a cubic response 
but is limited by flare light which is 
produced by dispersion in the phosphor 
and internal reflections in the glass 
face plate. When viewed in a darkened 
room a range in the order of 100:1 in 
screen luminance may be realized. 
Ambient illumination under more 
normal viewing conditions will result 
in considerable reduction in this range. 
It will be noted that under the best 
viewing conditions the range of the 
video signal which produces the 
maximum useful range of kinescope 
screen luminance is approximately 10:1. 
This depends to a large extent upon the 
level established for black signal. The 
extent of the variations has been dis- 
cussed by Schade. 12 

In this diagram the transfer charac- 
teristics of the overall system have been 
constructed by transferring the relative 
signal current to the plot of the amplifier 
characteristic to find the relative grid 
signal applied to the kinescope, then 
transferring this to the kinescope charac- 
teristic to determine the screen luminance 
and plotting this value over the original 
point on the camera characteristic. 
The dotted line shows the process for 
one point on the characteristic obtained 
from an iconoscope and a linear ampli- 
fier. 

This diagram shows the excessive 
white compression usually obtained from 
an uncompensated iconoscope. It also 
shows the extreme compression of the 
shadows and excessively high contrast 
in the remainder of the tonal range 
which is obtained from an uncompen- 
sated linear device. It will also be 
seen that the characteristic obtained 
with a device having a half-power law 
response is a fair approximation of the 
selected corrected response. 

The amplifier characteristics required 
to compensate the characteristics shown 
at (a), (b) and (c) in Fig. 7 to the 
response indicated at (d) are plotted 



Herbst, Drew and Johnson: Electrical and Photographic Compensation 295 



ou 
U 60 
O 
Z 4.O 








/ 














y 


^ 


2 


f 


do u 



4.O Z 


i * 

Z "0 


Kir 


ESCi 


>PE/ 






0> 


/ERX 


^L 


L / 


/ 




*''/ 


V 




00 

, Z 


do 






/ 
























CO. 








/ 
















/ 


fa 


/ 




10 ^ 


-J ft 






/ 1 










/ 






^ f 




/ 




A -J 


UJ 4. 




> 










1 




/ 


/ 


/ 


1 


fe) 




O 


UJ ^ 

a: 
o p 




/ 










I/. 


;/ 




/ 




1 






4 Qj 
ui 
P (* 


o * 

1 


^x 


7 












/ 


r 




^ 


' 






; ^ 




i 


L ^ 


h i 


i 


O 


< 


1 ' 


\. 


e 




o a 


4 


8 


3 


00 



GRID VOLTS 



ORIGINAL LUMINANCE 




<0 

4 8 IO / E 4 6 10 ao 40 do lo'o 

GRID VOLTS ORIGINAL LUMINANCE 

Fig. 7. Contribution of system elements to overall transfer characteristics. 



(a) Overall response with iconoscope and 
linear amplifier 

(b) Overall response with half-power law 
vidicon and linear amplifier 

(c) Overall response with linear device 
(ex: flying spot scanner) and linear 
amplifier 

(d) Overall characteristic after correction 



(e) Amplifier response for correcting icono- 
scope characteristic 

(f) Amplifier response for correcting half- 
power law characteristic 

(g) Amplifier response for correcting 
characteristic of linear pickup device 
NOTE: Broken parts of (d) & (e) illus- 
trate effect of simple "white" stretching. 



(All quantities in arbitrary units) 



at (e), (f) and (g), respectively. In 
order to provide a simple method of 
relating the various characteristics to 
the overall system response the positions 
of the dependent and independent 
variables have been inverted from their 
usual relationships in plotting the ampli- 
fier characteristics. Partial compensa- 
tion of the transfer characteristic ob- 
tained with an iconoscope has been 
obtained by expanding the signal in 
the range corresponding to the high- 
lights. The design and performance 
of such amplifiers has been discussed 



by Goodale and Townsend. 9 When 
the system employs simple "white 
stretching," the lower portion of the 
amplifier characteristic is linear. The 
characteristic of such an amplifier is 
shown by the dotted departure from 
Curve (e). The effect is to provide 
better rendition of the highlights at some 
expense in overall range and the dis- 
tortion of the characteristic in the 
shadows as shown by the dotted depar- 
ture from Curve (d). The transfer 
characteristics of the compensating am- 
plifiers are plotted on a linear scale in 



296 



October 1951 Journal of the SMPTE Vol.57 



100 



FOE LINEAR D LVICE. 






LINE.AR 
AH1PLIFIE.I 



LINEAB 
WITH WHf 



FOR 
ONOSCOPE 



AMPLIFIER 





STBElTCHlNG- 



ao 40 eo ao 

INPUT SIG-NAL (AfcfttTB.ARV UNITS) 



100 



Fig. 8. Transfer characteristics of correcting amplifiers. 




40 



A- 8 10 

ORIGINAL LUMINANCE 
(ARBITRARY UNITS) 

Fig. 9. Signal-to-noise ration of television pickup devices. 



60 100 



Fig. 8. The extent to which such 
compensation of the transfer charac- 
teristic can be employed again depends 
to a large extent upon the increase in 
noise level. Depending upon the lumi- 
nance range in which they appear, 
spurious signals may also be aggravated 
by such compensation. 



Effect of Electrical Compensation 
on Noise 

Assuming that the various television 
pickup devices are capable of providing 
a signal-to-noise ratio of 100:1 in the 
highlights the fluctuation noise in the 
reproduced picture may be calculated 



Herbst, Drew and Johnson: Electrical and Photographic Compensation 297 



u 

<o 

So 
-!Z 40 



tjh 30 
O_J 

P 

id* 



10 



zo. 

i 




FLYING- SPOT 



DE\ 



SCANNER- 



iciia 



AMPLIFIER LIMITED 
(ICON DSCOPE$ VIDICONS) 



4 6 10 20 

SCREE.N LUMINANCE. 

CARBITRARY UNITS) 



40 



80 100 



Fig. 10. Fluctuation noise in television screen (no compensation-linear amplifier). 



* 







Fig. 11. Fluctuation noise in 
television screen after compen- 
sation of transfer characteristics. 



I 2 4 8 10 20 40 

SCREEN LUMINANCE (ARBITRARY UNIT 



1 



100 



by considering the slopes of the amplifier 
and monitoring kinescope at each level 
of screen luminance. The effect in 
terms of peak video signal to rms noise 
level in the output of the pickup devices 
is shown in Fig. 9. The manner in 
which these characteristics are modified 
by the transfer characteristic of the 
monitoring kinescope is illustrated in 
Fig. 10 which shows the calculated 
fluctuation noise plotted against kine- 
scope screen luminance. Because the 
screen luminance is used as the abscissa 
there is no difference between the ap- 
parent noise from any of the amplitude 
limited devices. This is because the 
amplitude of the noise applied to the 



grid of the kinescope is constant and 
independent of the signal current from 
the pickup tube. The signal-to-noise 
ratio in the reproduced picture is there- 
fore dependent upon the shape of the 
kinescope characteristic rather than upon 
the response of the camera tube 
employed. It will be noted that the 
combination of the reduced camera 
noise at lower signal levels and the 
reduced slope of the kinescope charac- 
teristic in this region result in an im- 
proved signal-to-noise ratio in the 
shadows. This plot does not indicate 
the serious distortions in contrast rendi- 
tion which accompany the use of un- 
compensated linear devices. 



298 



October 1951 Journal of the SMPTE VoL 57 



























^ 

.1 


























OK 


IG-IMA 


_ STE 


P WE! 


5GE^ 


























V 






















































^ 


















""^ 














\co 


> 

MBINA' 


noN c 


F oei 


>INA\- 










^"^ 






L^ 








Wl 


.DG-E 


VND H 


ASK. 








~^ 






























V 




\ 




/"* 


IT OF 


FOCU 


S MAS 


K. 




















/ 














>y 


















V 




V 









Fig. 12. Principle of area masking illustrated by detail on step wedge. 



When electrical compensation for the 
transfer characteristic is introduced the 
noise is modified by the slope of the 
amplifier characteristic at each screen 
brightness level. The effect in the re- 
produced television image is illustrated 
in Fig. 11. In the case of the icono- 
scope the amplifier slope is reduced in 
the shadows and increased in the high- 
lights. The net result is a serious 
increase in the noise in the highlights. 
The opposite is true for the other types 
of pickup devices all of which require 
expansion of the lowlight signals and 
compression of the signal in the high- 
lights. The very serious increase in 
apparent noise in the shadows in the 
case of a linear device which is limited 
by amplifier noise is shown by the 
characteristic for the linear vidicon. 

The subjective difference between 
noise in the highlights and noise in the 
shadows has not been considered in this 



discussion. Likewise, the curvature of 
the kinescope screen in the region of the 
highlights has been neglected in making 
these calculations. The results, however, 
are sufficient to indicate that the toler- 
ance in apparent noise is insufficient to 
permit optimum compensation for both 
transfer characteristic and aperture losses 
to be applied without serious increase 
in the apparent graininess of the tele- 
vision image. Improvement in the 
signal-to-noise ratio of the pickup de- 
vices will raise the level of these noise 
characteristics without greatly modifying 
their general shape. 

Photographic Area Masking 

Working in a different field, G. L. 
Dimmick and H. E. Haynes found that 
the tonal range in high-contrast prints 
could be successfully reduced without 
impairment of the detail contrast and 
suggested that this technique, which has 



Herbst, Drew and Johnson: Electrical and Photographic Compensation 299 




Fig. 13. Original negative. 




300 



Fig. 14. Normal contrast print from negative in Fig. 13. 
October 1951 Journal of the SMPTE Vol. 57 




Fig. 15. Print processed to lower than normal contrast from negative in Fig. 13. 




Fig. 16. Unsharp mask from original negative in Fig. 13. 
Herbst, Drew and Johnson: Electrical and Photographic Compensation 30 1 



been applied to some extent in the 
graphic arts, might be applied to tele- 
vision reproduction with equal success. 
A brief investigation disclosed that this 
photographic method could be advan- 
tageously applied to the processing of 
prints intended for transmission over the 
television system. 

The technique which is known as 
"Area Masking" is not new since there 
is evidence that it was described by 
German experimenters as early as 1931. 
More recent work with unsharp masks 
was described by M. J. Johnson 10 in 
1943, while a review of the principles 
and methods of obtaining the effect was 
published by J. A. G. Yule of Eastman 
Kodak Co. in 1945. 11 Recently, this 
method has found some application in 
the graphic arts where it is often necessary 
to reduce the wide tonal range of a pic- 
ture from contrast ratios of 100:1 or 
greater in the properly processed trans- 
parency to a range of 20 : 1 or less for 
proper reproduction within the limita- 
tions of papers and inks. The limitations 
of the television system impose similar re- 
strictions on the tonal range which can 
be adequately accommodated since, al- 
though the previous discussion referred to 
realizable ranges of 100: 1 these can only 
be achieved under the most favorable 
conditions and are seldom attained in 
practice. A more realistic range of 30 : 1 
seems to coincide with current informed 
opinion. Since motion picture posi- 
tives, properly processed for direct pro- 
jection, frequently contain ranges of con- 
trast in excess of 1 50 : 1 the conditions 
for televised film are similar to those 
encountered in the reproduction of pic- 
torial material by half-tone printing. 

A mask may be considered as a photo- 
graphic image which is superimposed on 
another photographic image to alter the 
characteristics of the final reproduction. 
If a positive transparency, processed to a 
low control gamma, is placed over the 
negative from which it was made, the 
contrast range is less than that in the 
original, and prints made from this com- 



bination on normal print stock with nor- 
mal processing will contain a reduced 
contrast range. If the mask is in sharp 
focus and exact register, the net effect is 
that of processing the final print to a 
lower control gamma. However, if the 
image is intentionally defocused when the 
mask is made, the large area contrast 
will be reduced but the detail contrast 
will remain unchanged since the mask in 
any given area will act as a neutral filter 
for sharp detail, reducing the exposure of 
the final transparency but not affecting 
the detail contrast ratio. Such an un- 
sharp mask can be made by separating 
the emulsion, which will constitute the 
mask, from the negative during exposure 
by a distance sufficient to produce 
appreciable blurring. 

The principle may be illustrated by 
considering the effect on a step wedge 
having fine detail in each step. In Fig. 
1 2 the original step wedge is considered to 
consist of five equal logarithmic steps 
covering a total overall contrast range o 
100:1. The fine detail in this wedge is 
represented by the edges and the fine 
lines centered in each step. The un- 
sharp mask is represented as having an 
overall contrast range of 10:1. The 
edges are reproduced by gradual transi- 
tions since the image is out of focus, while 
the fine detail in the center essentially 
disappears. The combination of the 
original transparency and the mask pro- 
duces a step wedge in which the overall 
contrast is 10: 1 while the contrast excur- 
sions at the edges and in the fine lines re- 
main unchanged. It will be noted that 
in this figure the detail is shown as hav- 
ing a contrast excursion of one-half the 
contrast between successive steps in the 
original wedge. In the combination the 
detail contrast is equal to the contrast be- 
tween steps while the edges are repro- 
duced at the original contrast. This 
also serves to illustrate the edge effect 
which is produced by the process and 
which can result in extreme artificiality 
in the final transparency if the method is 
carried to extremes. In practice, it is 



302 



October 1951 Journal of the SMPTE Vol.57 



probable that the mask would be applied 
to the negative during the printing proc- 
ess. Under special circumstances the 
mask could be applied to the positive 
print when televised. 

The television engineer will recognize 
the analogy to "high peaking" which is 
employed in electrical aperture compen- 
sation. The edge effects are similar to 
those produced by the transients or 
"overshoots" in electrical networks. 
Schade 4 has pointed out this analogy and 
treated the effect in some detail. Yule 11 
has pointed out that this accentuation of 
the edges is similar to the subjective re- 
sponse of the eye when viewing adjacent 
contrasting areas and does not impair the 
natural appearance of the reproduced 
image unless excessively aggravated. 

The process may be likened to auto- 
matic dodging during the printing proc- 
ess, each area being given the proper ex- 
posure to place it in the desired region of 
a reduced tonal scale. In effect, the 
process gives the impression of more even 
scene lighting while permitting natural 
illumination during the filming of the 
original scene. The method requires the 
production of an extra print and adds 
another step in the photographic proc- 
ess. The resultant improvement in the 
quality of the televised film appears to 
justify this additional effort. 

The exact parameters to be applied 
during processing have not, as yet, been 
determined. However, the method does 
not appear to be critical since the very 
first attempts met with excellent success. 
The degree of defocusing which will be 
optimum for reproduction over the tele- 
vision system may be different from that 
which is best suited to direct viewing of 
an opaque print. The possible over- 
accentuation of detail contrast to compen- 
sate for aperture losses in the television 
system remains to be investigated. Be- 
cause the mask is appreciably out of fo- 
cus, serious registration problems are not 
anticipated and have not constituted a 
difficulty in the tests made to date. 
There seem to be no special difficulties in 



the employment of the process to obtain 
prints better suited to the characteristics 
of the system although further refine- 
ments may provide improved means of 
control and closer realization of optimum 
quality. 

It will be noted that the process ac- 
complishes the desired reduction in ex- 
cessive contrast and compensation for 
aperture losses in one photographic step 
and that this is accomplished without 
any increase in noise except for the addi- 
tional film graininess introduced by the 
mask. In our experiments this increase 
in grain has not been noticeable. The 
method therefore allows greater latitude 
for the introduction of such remaining 
compensation of transfer characteristic 
by electrical means as may be considered 
desirable. 

Pictorial Effect of Area Masking 

The effect on the picture quality can 
be judged from a series of reproductions 
made from 35-mm transparencies. It 
should be borne in mind that the illus- 
trations shown here are half-tone repro- 
ductions of glossy paper prints which in 
turn were made from original transparen- 
cies. Transparencies demonstrate the 
principle of photographic area masking 
effectively but much information has 
been lost in the glossy print and half-tone 
processes which seriously limit the con- 
trast range. Figure 1 3 is an original 35- 
mm normal contrast negative. A direct- 
contact print taken from this negative 
and processed for direct projection was 
found to have a transmission range of 
130:1 (Fig. 14). This print is too con- 
trasty to reproduce well over the tele- 
vision system. Figure 1 5 shows the effect 
of processing the print to lower than nor- 
mal contrast. In this print, the overall 
contrast range was reduced to 10:1. It 
will be noted that the detail is lacking 
and the extreme flatness produces a 
chalky or veiled appearance. 

Figure 16 shows a positive unsharp 
mask which when combined with the orig- 
inal negative produces a contrast range 



Herbst, Drew and Johnson: Electrical and Photographic Compensation 303 




Fig. 17. Area masked print from original negative in Fig. 13 
and un sharp mask in Fig. 16. 




304 



Fig. 18. Photographic reproduction of the original normal contrast 
transparency of Fig. 14 over an iconoscope television system. 

October 1951 Journal of the SMPTE VoL 57 






31 




Fig. 19. Photographic reproduction of low contrast transparency 
of Fig. 15 over an iconocsope television system. 




Fig. 20. Photographic reproduction of area masked transparency 
of Fig. 17 over an iconoscope television system. 

Herbst, Drew and Johnson: Electrical and Photographic Compensation 305 



KINESCOPE 
MONITOB 



SEMI -SILVERED 
MlttBOC 




f> RECORDING- CAMEBA 
5HABP IMAGE 

OUT-OF- FOCUS IMAG-E 

TELEVISION PICKUP TUBE 
(VIDICON PROPOSED) 



LARG-E. AREA CONTROL 61G-NAL 



VIDEO 5IG-NAL INPUT 

Fig. 21. Electrical area masking. 



of 10:1 in a normally processed print. 
The print obtained by this area masking 
process is shown in Fig. 17. It will be 
noted that although the tonal range is 
the same as in the print made by reduc- 
tion of the control gamma, the detail 
contrast is unimpaired. Although the 
appearance in direct projection is not as 
pleasing as the more contrasty original 
print, the fine detail is retained and the 
picture still has the quality loosely 
termed "snap" or "crispness." 

The reproduction of the original nor- 
mal contrast transparency shown in Fig. 
14 over an iconoscope channel is shown 
in Fig. 18. This is a photograph of a 
5-inch monitor having a Pll phosphor 
and operated over the optimum range of 
its characteristic. A 4 X 5-in. still 
camera was employed to eliminate any 
losses in detail by the recording process. 
It will be noted that both the highlights 
and the shadows are excessively com- 
pressed. Figure 19 is a photograph of 
the same monitor when the low-contrast 
transparency shown in Fig. 15 is tele- 
vised over the same channel. The only 
change in the settings was to increase the 
gain to obtain the same video signal at 
the grid of the kinescope. The loss of 
detail is very apparent, especially in the 
highlights. Figure 20 is the result of 



televising the area masked transparency 
shown in Fig. 17. The good rendition of 
the entire tonal range and the improve- 
ment in detail are apparent. 

The method, in its present state of de- 
velopment, has recently been demon- 
strated to representatives of several 
broadcasting companies who expressed 
considerable interest in its possibilities. 
Efforts are currently under way to apply 
the technique to both 16-mm and 35-mm 
motion picture film. It is of particular 
value in cases where access to the original 
negative is possible such as in the case of 
preparing advertising trailers and other 
material intended solely for reproduction 
over the television system. 

It should be noted that the method is 
applicable to electrical circuits. One 
method of applying the technique to 
video recording is illustrated in Fig. 21. 
This is a block diagram showing the re- 
cording camera disposed properly in 
front of the kinescope monitor. By 
means of a semi-silvered mirror or other 
light-splitting device an out-of-focus 
image is focused on the photosensitive 
surface of a pickup tube. The signal 
from this tube represents the contrast in 
the large areas and is used to control the 
gain of an amplifying device. This cir- 
cuit is equivalent in its operation to the 



306 



October 1951 Journal of the SMPTE Vol. 57 



photographic mask. It will be noted 
that the gain varies with the signal level 
produced by the larger picture areas but 
is constant at any level as regards the 
higher-frequency signals representing the 
fine detail. The full advantage of the 
masking technique in achieving compen- 
sation without aggravating the noise is 
not realized in the simple circuit illus- 
trated in Fig. 21. 

Conclusion 

The characteristics employed in this 
discussion are given as representative of 
the performance of several types of tele- 
vision pickup devices. In practice, wide 
variations may be observed. The actual 
measured figure of aperture response, 
transfer characteristic and signal-to- 
noise ratio may differ from those given 
since individual tubes and the conditions 
of operation are variable. Furthermore, 
further improvements in tube perform- 
ance may modify any specific conclusions 
drawn from the foregoing. 

At the present time the limitations of 
the television system make some form of 
compensation highly desirable. Unfor- 
tunately, currently available elements do 
not provide sufficient latitude for the in- 
corporation of optimum electrical com- 
pensation. The principle of area mask- 
ing therefore appears to offer attractive 
possibilities especially in the preparation 
of motion picture positives specifically in- 
tended for transmission over the television 
system. 

References 

1. O. H. Schade, "Electro-optical charac- 
teristics of television systems, Part I: 
Characteristics of vision and visual 
systems," RCA Rev., vol. IX, no. 1, 
pp. 13-37, Mar. 1948. 



2. O. H. Schade, "Electro-optical charac- 
teristics of television systems, Part II: 
Electro-optical specifications for tele- 
vision systems," RCA Rev., vol. IX, 
no. 2, pp. 245-286, June 1948. 

3. O. H. Schade, "Electro-optical charac- 
teristics of television systems, Part III: 
Electro-optical characteristics of 
camera systems," RCA Rev., vol. IX, 
no. 3, pp. 490-530, Sept. 1948. 

4. O. H. Schade, "Electro-optical charac- 
teristics of television systems, Part IV : 
Correlation and evaluation of electro- 
optical characteristics of imaging sys- 
tems," RCA Rev., vol. IX, no. 4, pp. 
653-686, Dec. 1948. 

5. E. D. Cook, "The aperture effect," 
Jour. SMPE, vol. 14, pp. 650-662, 
June 1930. 

6. M. Cawein, "Television resolution as 
'a function of line structures," Proc. 

IRE, vol. 33, pp. 855-864, Dec. 1945. 

7. R. B. Janes, R. E.Johnson and R. S. 
Moore, "Development and perform- 
ance of television camera tubes," 
RCA Rev., vol. X, no. 2, pp. 191-223, 
June 1949. 

8. R. B. Janes and A. A. Rotow, "Light 
transfer characteristics of image orthi- 
cons," RCA Rev., vol. XI, no. 3, pp. 
364-376, Sept. 1950. 

9. C. L. Townsend and E. D. Goodale, 
"The orthogam amplifier," RCA Rev., 
vol. XI, no. 3, pp. 399-410, Sept. 
1950. (Abstract in Jour. SMPTE, 
vol. 56, pp. 76-78, Jan. 1951.) 

10. M. V. Johnson, "Print control with 
blurred positive masks," Am. Phot., 
vol. 37, pp. 14-16, Mar. 1943. 

11. J. A. C. Yule, "Unsharp masks," /. 
Phot. Soc. Am., vol. 11, no. 3, pp. 123- 
132, Mar. 1945. 

12. O. H. Schade, "Image gradation, 
graininess and sharpness in television 
and motion picture systems, Part I: 
Image structure and transfer charac- 
teristics," Jour. SMPTE, vol. 56, pp. 
137-177, Feb. 1951. 



Herbst, Drew and Johnson: Electrical and Photographic Compensation 307 



Processing 16-Mm Kodachrome 
Prints 

By WILLIAM HEDDEN, THOMAS WEAVER and LLOYD THOMPSON 



In 1949, the Eastman Kodak Company agreed to license independent labora- 
tories to process 16-mm Kodachrome film. The first machine for this purpose 
has been built by The Calvin Company, and has been in use since April 1, 
1950. This paper gives a description of the machine, some of the problems 
encountered with the process, and some of the results obtained. 



VV HEN Eastman Kodak Company 
arranged to license independent labora- 
tories to process 16-mm Kodachrome 
film, The Calvin Company decided to 
construct such a machine for 5265 stock. 
This decision was made for several rea- 
sons: 

(1) It was desirable that we eliminate 
the necessity of sending all printed dupli- 
cates to the Chicago laboratory of East- 
man Kodak Company for processing, as 
this caused delays even though air freight 
was used in both directions. 

(2) The cost of shipping this material 
back and forth by air, and the necessary 
telephone calls, etc., was expensive. 

(3) It was believed that the control of 
processing quality within our own organ- 
ization might lead to improved color 
quality in Kodachrome duplicates, be- 
cause of closer coordination between 
printing and processing. 



Presented on April 30, 1 951 , at the Society's 
Convention in New York, by William 
Hedden, Thomas Weaver and Lloyd 
Thompson, The Calvin Company, 1105 
Truman Rd., Kansas City, Mo. 



It was realized that this was a project 
of rather large scope. The installation 
would be difficult and expensive, and 
only a very limited amount of technical 
experience was available to independent 
laboratories. Such an installation would 
be somewhat different from the facilities 
of the Eastman laboratories, and no one 
could accurately predict what might 
happen. 

The machine was planned and com- 
pleted in about a year's time. Since 
April 1, 1950, all Kodachrome duplicates 
made by us have been processed in our 
own machine. While the basic process- 
ing information was made available by 
the Kodak Company in a manual for 
licensees, it was decided to modify the 
machine design. 

We felt the Kodachrome machine 
should be built on the same basic design 
as our black-and-white machines, so that 
operators familiar with the black-and- 
white equipment could also run the color 
machine. Such a machine was easier 
for us to build, and certain parts were 
interchangeable with the black-and- 



308 



October 1951 Journal of the SMPTE VoL 57 




General view of Kodachrome processing machine. 




Looking toward dry end of machine. In the foreground can be seen one of the 
color printers with the second one in about the center of the machine. 



Hedden, Weaver and Thompson: Kodachrome Prints 



309 



white machines. It was decided to oper- 
ate our equipment at higher machine 
speed than the Kodak machines, in order 
to get additional production capacity. 

After gathering as much information as 
possible, Bob Sutton and our Engineering 
Department proceeded to make a layout 
of a machine based on the information 
released by Eastman Kodak Company, 
and similar to our black-and-white proc- 
essing machines which were originally 
designed following the plan of the Ansco 
black-and-white machine. This ma- 
chine is an adaption of the modified 
Spohr-Thompson bottom-rack drive, and 
runs at 62 fpm. 

Developing time of the various solu- 
tions was a factor in determining tank 
size, and the number of racks necessary 
for operation. A few extra tanks were 
added as a safety factor in event of a proc- 
essing change. The racks and tanks 
were designed so that it would be com- 
paratively easy to change tanks in order 
to make timing or processing solution 
changes. 

The machine as finally constructed 
consists of nineteen stainless steel (type 
316) tanks. The ferricyanide bleach 
tank is lead lined, and the rack in the 
bleach is made of red brass. Twenty- 
nine racks are used in normal operation 
of the process. A 2-hp, 3-phase motor 
supplies the power through a belt to the 
drive shaft. The drive shaft consists of a 
length of 1-in. shafting with one worm 
gear at each rack position enclosed in a 
sealed oil -filled gear case. Each worm 
gear drives a spur gear, and another spur 
gear is placed on this shaft above the gear 
case. When the racks are in position on 
the machine, the upper rack gear is 
meshed with the spur gear outside the 
gear case, and this drives the rack. Pins 
are used to keep the racks in proper posi- 
tion. Individual racks can be removed 
from the machine simply by lifting them 
out. 

The bottom rollers of the drying cabi- 
net are driven by means of a chain drive 
attached to the end of the main drive 



shaft. The drying cabinet uses a closed 
circuit of air in order to maintain the 
proper drying conditions. The humidity 
is controlled by the use of a Frigidaire 
sealed J-hp condensing unit. The con- 
denser and the compressor unit are 
mounted in the air stream, reheating the 
air after it has been dehumidified by the 
cooling coil. This unit in conjunction 
with electric strip heaters, a blower and 
control instruments, maintains a con- 
stant relative humidity of 50% at a tem- 
perature of 85 F. 

The feed cabinet at the head of the 
machine is large enough to permit stor- 
age of stock for almost two minutes before 
the elevator reaches the top. 

The take-off elevator is equipped with 
a brake which prevents rollback when 
take-off pressure stops. The take-off 
spools are driven by a torque motor to 
maintain constant take-up pressure. 
The motor has a separate operating 
switch so that it may be shut off momen- 
tarily while the film is being changed 
from one spool to another during that 
time the elevator takes up the film. 

The basic rack used in the machine is 
made of stainless steel angles, hard rub- 
ber rollers and Synthane bearings. 
Separators are placed between each of 
the 19 bottom drive rollers to prevent 
looping. The upper 20 rollers are fitted 
loosely to their shaft, and the total capac- 
ity of each rack is 126 ft. 

To aid in the removal of the antihala- 
tion backing of the film, buffer rollers are 
installed in the first three washes. A 
Canton flannel-covered wooden roller is 
suspended between the top and bottom 
rollers of a rack. This roller, driven by 
the rack drive shaft in the same direction 
of film travel, buffs the film base remov- 
ing all the backing. 

It is necessary to expose the cyan and 
yellow layer in the film separately before 
color developing; therefore, it was essen- 
tial that we build a cyan and yellow 
printer. 

In the Kodak processing machine the 
film runs horizontally over the printers, 



310 



October 1951 Journal of the SMPTE Vol.57 




mmr* 



Waxer, elevator and take-ups. 
Take-ups are driven by torque motor. 

but the printer which was designed for 
our machine was built so that the film 
travels in a vertical position. Basically 
the printer consists of a lamp, centering 
light through an intergrading bar and 
filter, exposing the film as it travels 
through a masked channel. Power for 
the lamp is fed from transformers and 
adjusted by means of a Variac trans- 
former. The intensity is measured with 
a foot-candle meter, and also checked by 
the means of an ammeter. An Aklo 
glass was installed in the blue printer to 
prevent heat from cracking the filter. 
Blowers are installed on each printer to 
carry off the heat from the lamp. An air 
squeegee is used before the film enters 
the sound applicator, and another is used 
just before it enters the drying cabinet. 
At several points throughout the machine 




Mechanism for applying sodium sulfide 
to sound-track area. 

small rubber wiper squeegees are used to 
prevent dilution and carryover from one 
tank to another. 

Perhaps the most difficult processing 
operation to perfect was the sound track 
application. To develop the sound track 
on Kodachrome prints the film passes 
edgewise on an applicator wheel, while a 
sulfide sound developing solution is 
applied just to the edge area of the pic- 
ture by a wiper knife blade or pen. 
This is done just before the magenta de- 
veloping solution. After the sound de- 
veloping solution has reacted a few sec- 
onds it is necessary to wash it from the 
film immediately to prevent any sulfide 
sound solution from fogging the picture 
area. Several methods of doing this 
were tried before a satisfactory system 
was found. The problem was finally 
solved by the use of vertical wash jets 
hitting the film at an angle, which 
allowed the water to flow across the 
track area and off the film immediately. 
While a manual of instructions was sup- 
plied by Eastman Kodak Company, the 
increased speed of our machine presented 



Hedden, Weaver and Thompson: Kodachrome Prints 



311 



an application problem not encountered 
on machines operating at lower speed. 
With an efficient squeegee before the 
sound applicator, the film was still too 
moist when it entered, and uneven appli- 
cation of the sulfide sound solution re- 
sulted. To overcome this problem it was 
necessary to use one of the extra tanks 
and racks as a dry box, which we call the 
"hot rack." The film is dried enough so 
that uniform sound application is pos- 
sible. Once these problems were solved, 
very little trouble has been encountered 
with sound application. 

Constant replenishment of the solu- 
tions is accomplished by the means of 
adding solutions controlled by stainless 
steel needle valves, and measured 
through a Stabil vis Flowra tor which meas- 
ures and shows the exact amount of re- 
plenisher being added at all times. This 
mixes with the tank solution being re- 
circulated just before it enters the pump. 
It is then filtered, passed through a heat 
exchanger and another Flowrator which 
shows the rate of circulation, and then 
enters the system by means of a pipe at 
the bottom of the tank. Any excess de- 
veloper which is not used overflows into 
the sewer by means of a pipe at the de- 
sired tank level. 

A small pot made of stainless steel is 
placed on the system between the replen- 
isher valve and the recirculation pump 
for the addition of chemicals for process 
correction while the system is in opera- 
tion. By using this method, it is possible 
for the Control Department to make 
additions from the outside of the process- 
ing room. It also insures proper mixing 
and minimizes the danger of streaking 
film by improper handling. 

Brown temperature controls are used 
to maintain temperature within plus or 
minus one-half degree at 80 F. All solu- 
tions, including the wash water, are auto- 
matically controlled at 80 F. Automatic 
temperature control devices are used to 
mix the proper amount of cold and hot 
water to maintain the temperature of 
solution and wash water. 



The amount of wash water being used 
in each tank is also accurately controlled, 
and measured by Flowrators. All the 
developer solutions are recirculated and 
filtered with the exception of the pre- 
hardener, ferricyanide bleach, and hypo. 

The filter is a cast-iron pot with a 
clamp-tight cover. The insert, or filter, 
consists of a perforated stainless-steel tu- 
bular holder, covered with a fine stain- 
less-steel screen. This is wrapped with 
Filtocot, and finally a layer of gauze is 
tied around the outside to prevent any 
cotton from coming loose and getting into 
the system. The pump forces the solu- 
tion around and through the filtering 
material to the center of the holder where 
it leaves through a pipe connected to the 
bottom of the filter holder. 

The replenisher solutions are mixed in 
stainless steel mixing t#nks on the floor 
above the processing machine, and flow 
to the machine by gravity. Each mixing 
tank is provided with a reserve tank of 
sufficient size to provide the machine 
with replenisher while a new tank of solu- 
tion is being mixed. Lighting mixers are 
provided for all mixing tanks. The 
bleach tank is lead -lined and equipped 
with Saran pipes and red brass valves. 
Ventilation is provided for the scales used 
in weighing organic developers and 
couplers. 

In order to get a consistent process it is 
necessary to provide regular mainte- 
nance. During the first month of oper- 
ation considerable machine maintenance 
was required, due to the formation of or- 
ganic tars in some color developers. 
These tars required that the color de- 
veloper racks be removed from the ma- 
chine each night for cleaning, and clean- 
ing tanks were designed for this purpose. 
One tank holds an acid-alcohol bath, and 
the other a water-rinse bath. However, 
improvements in the process during the 
last year, along with operating experi- 
ence in handling color developers, has 
greatly reduced the tar formation origi- 
nally encountered. These improve- 
ments reduced the amount of rack clean- 



312 



October 1951 Journal of the SMPTE Vol.57 




.1 



Jet wash for removing sodium 

sulfide from sound track before 

processing continues. 

ing necessary, and have decreased much 
of the rack maintenance which was re- 
quired when the racks received a great 
deal of handling. 

It has been found that frequent filter 
changes in the solution recirculating sys- 
tem are good economy. Clean filters 
provide solutions which are free from tar 
and sediment and not only provide 
cleaner, more even development, but are 
also a factor in reducing rack cleaning 
and maintenance. Other parts of the 
machine must be given regular mainte- 
nance and cleaning in order to insure ac- 
curate readings and accurate perform- 
ance. Filter changing and gauze clean- 
ing are regular maintenance. 

Color processing introduced the neces- 
sity of protecting operating personnel 
from skin irritation, or dermatitis, aris- 




Part of the control instruments 
to regulate temperature, rate of 
replenishing and rate of agitation. 



ing from the use of particular types of 
organic chemicals. Eastman Kodak 
Company provided considerable infor- 
mation and suggestions for protection in 
the use of chemicals, and by following 
these suggestions explicitly, dermatitis has 
not been a problem. Naturally, a few 
people had to learn the hard way, but 
once they learned it simply was not a 
problem. 

A problem was presented in the dis- 
posal of used filter packing. Used pack- 
ing is saturated with organic tars and 
concentrated developing by-products. 
Special disposal procedures were re- 
quired to prevent skin irritation to those 
outside the company handling this refuse. 

Usually the best black-and-white film 
operators graduate to the color machine, 
after being trained as black-and-white 
film operators. Although operation of 
color and black-and-white machines is 
generally similar, color processing re- 
quires more detailed machine work, and 
generally more alert operation than does 
black-and-white processing. 



Hedden, Weaver and Thompson: Kodachrome Prints 



313 



The importance of responsible solu- 
tion-mixing men was established early in 
our color processing experience. While 
small errors may not necessarily be seri- 
ous in black-and-white mixing, they be- 
come disastrous in color. Inaccurate 
solution mixing often will not appear as 
trouble until the solution has been in use 
for several hours, thus presenting difficult 
problems of trouble shooting and correc- 
tion which may result in considerable 
loss of production processing time. 

Specially trained chemists for solution 
control and analysis are also necessary. 
Analysis of replenishers immediately after 
mixing and before use is desirable, as is 
regular analysis of tank concentration. 
Analytical personnel are especially valu- 
able when trouble shooting is required. 

Color control is perhaps the most 
important processing responsibility. 
Usually supervisory personnel undertake 
this control work. They must be thor- 



oughly trained in all phases of color proc- 
essing, and have complete knowledge 
and experience in the operation of the 
machine and other equipment used. 

Specifically, our- control procedure 
consists of three steps: Sensitometric 
tests, picture strips, and print inspection. 
Drum-printed sensitometric tests are pro- 
cessed regularly, read on an Ansco color 
densitometer and recorded. Backing up 
this sensitometric information are printed 
picture strips developed with each sensi- 
tometric test. 

Occasionally these picture strips show 
conditions not interpretable on the sensi- 
tometric test, and this is extremely prac- 
tical for quality checking. Visual in- 
spection of prints as soon after processing 
as possible is another valuable and prac- 
tical method of quality control. Inspec- 
tion also provides a quick check on the 
printing operation. By combining infor- 
mation obtained from these three sources, 




314 



A part of the chemical control laboratory. 
October 1951 Journal of the SMPTE VoL 57 



it is possible to hold Kodachrome print 
quality within narrow and acceptable 
limits. 

We use one group of printers, one proc- 
essing machine, and by having both the 
printing and processing of Kodachrome 
film within the same laboratory, it has 
been possible to achieve noticeable im- 
provement in the consistency of color 
quality release printing. Such consist- 
ency, is noticeable in regular printing, but 
it shows up immediately and noticeably 
when it is necessary to print hard to re- 
produce material, such as to make prints 
from masters. 

It would not be proper to end this pa- 
per without mentioning a few of the peo- 
ple who have been extremely helpful in 
the project from the very beginning, al- 
though it will not be possible to list them 
all. We were very fortunate in having 
Bob Sutton and Ken Curtis in our Engi- 
neering Department, along with the men 



who helped them in building and install- 
ing the machine. Besides the authors, 
Dale Musselman spent a great deal of 
time and thought in getting the process 
started, maintaining quality, and turning 
out production in a minimum length of 
time with a minimum amount of spoil- 
age. The men who actually run the 
machine and mix the chemicals have 
been very interested in the process, and 
very helpful in their suggestions so that 
the best possible results could be ob- 
tained. It would be impossible to name 
personally all the people at the Eastman 
Kodak Company who have helped and 
encouraged us in getting the machine 
built and into operation. And, we 
would like to acknowledge and thank 
them and also the men at Ansco for their 
interest and suggestions in this project. 

We feel the project has been a success, 
and perhaps the greatest factor in that 
success is the pride of achievement felt 
by each person working on it. 



Hcdden, Weaver and Thompson: Kodachrome Prints 



315 



A System of Double Noise Reduction for Variable- 
Area Recording for Direct-Playback Purposes 



By J. G. STREIFFERT 



In variable-area recordings made for direct-playback purposes, the density 
of the "opaque" part of the track is established by distortion criteria and is 
usually so low that the signal-to-noise ratio is adversely affected. A system 
of "double noise reduction" is proposed which does not require the use of 
auxiliary lamps, slits or galvanometers. By this means, not only is the clear 
area of the track reduced during periods of low modulation, but also the 
density of the exposed area of the track outside the modulation envelope is 
increased in order to reduce the noise contributed by this part of the track. 
Tests indicate that a reduction in noise of 3 to 4 db can be expected. 



A T is WELL KNOWN that when variable- 
area recordings are made for direct- 
playback purposes, the density of the 
"opaque" portion of the track is usually 
undesirably low (1.0 or less), if the re- 
quirement of minimum distortion is met. 
Under these conditions, during repro- 
duction a substantial fraction of the 
incident light gets through the semi- 
opaque part of the track and adversely 
affects the signal-to-noise ratio. To 
ameliorate this difficulty, it has been 
proposed by Robinson, 1 Dimmick 2 and 
others, 3 that what might be called 
"double noise reduction" be used. A 
drawing illustrating what this type of 
track would look like is shown in Fig. 1. 
The clear area of the track would be 
reduced during periods of low modula- 



Communication No. 1418 from the Kodak 
Research Laboratories, a contribution 
submitted August 9, 1951, by J. G. 
Streiffert, Eastman Kodak Co., Roches 
4, N. Y. 



ter 



tion by application of noise-reduction 
currents to the recording galvanometer 
as is the custom in making direct- 
playback recordings. In addition, the 
outer portions of the track are made 
completely opaque by subjecting the 
region outside the modulation envelope 
to a higher-intensity exposure than the 
region which carries the modulation. 
Previous proposals for accomplishing 
this end have required the use of one or 
more auxiliary items, such as lamps, 
slits, galvanometers, etc., to lay down 
successive exposures. The proposals 
which follow indicate means for achiev- 
ing the required differential in exposure 
in the two parts of the track simultaneously 
and with a minimum of complication 
and of modification. 

The problem is that of realizing a 
higher-intensity exposure in the portion 
of the track which is normally occluded 
by the opaque noise-reduction shutter 
vanes than in the portion not occluded 



316 



October 1951 Journal of the SMPTE Vol.57 



Fig. 1. Drawing of a vari- 
able-area direct-positive 
recording with double 
noise reduction. 



Fig. 2A. Disposition of 
polarizers in optical 
system to produce higher 
intensity of exposure 
in outer portions of 
track than in central 
portions. 




Illumination 
at slit 



Lamp 



t 

Noise- 
reduction 

Polarizer A ' vanes 
Opaque 
mask 



Fig. 2B. Vectorial representation of light intensity 
after passing through 2 or 3 polarizers. 



by the vanes. Several solutions of this 
problem are suggested. 

In Figure 2A, polarizing means are 
shown in the condenser system on 
either side of the noise-reduction shutter 
vanes. In addition, the noise-reduction 
shutter vanes are made of either polariz- 
ing film or of a birefringent material, 
such as mica, which produces circularly 
or elliptically polarized light. The 
two polarizing disks are adjusted for 
partial extinction. By proper orienta- 
tion of the two disks relative to the 
shutter vanes, a condition is realized 
wherein the light intensity is greater 
where the beam traverses all three 
polarizing films than when it traverses 
only the two disks. This is shown 
vectorially in Figure 2B. If Oa repre- 
sents the plane of polarization of polar- 
izer A, and Oc that of polarizer C, then 
the intensity of light passing through 




these polarizers will be the projection 
of the vector, OA, on Oc, which is OC. 
However, where the light passes through 
the polarizing shutter vanes, the intensity 
is determined by the projection of OA 
and Ob, which is OB, and then the 
projection of OB on Oc, which is OC'. 
By adjusting the plane of polarization 
of the various polarizers, any ratio of 
intensity between OC and OC' from 
zero to one can be attained. This 
provides a means for adjusting the 
relative exposures in the two exposed 
portions of the track. 

Three other methods of attaining 
two exposure levels in the two parts 
of the track have been suggested by 
R. N. Carter. * These are shown in Fig. 3. 
In one method, the shutter vanes are 
made of semitransparent material and 



* Patent Dept., Eastman Kodak Co. 



J. G. Streiffert: Noise Reduction for Direct Playback 



317 




Semi-transparent 
^noise-reduction 
V shutter vanes 



Opaque mask 



Fig. 3. Overlapping shutter- vane method 
of obtaining differential exposure. 

overlap in the central region. For low 
levels of modulation, the overlap would 
be slight, and as the modulation in- 
creased, the vanes would move toward 
each other and overlap would increase. 
The central, modulated portion of the 
track would be exposed by light which 
had traversed two thicknesses of semi- 
transparent shutter material, whereas 
the outer regions of the track would 
be exposed by light which had traversed 
only one thickness of material. The 
ratio of exposures in the two areas 
would be determined by the transmission 
of the vanes and would not be readily 
adjustable. Adjustability would not 
appear to be very important, however, 
since the density of the outer regions of 
the track would not be critical, the only 
requirement being that it be high 
enough to be substantially opaque, i.e., 
2.0 to 2.5. If the photographic film is 
developed to a gamma of 3.0, this means 
that the outer regions of the track would 
have to have approximately four times 
the exposure of the modulated portions 
and that the shutter vanes would have 
to have a transmittance of 25%, or a 
density of 0.60. 

The use of shutter vanes made of 
different colored filters has also been 
proposed. The difficulty of selecting 
different colored filters which give 
substantially identical exposure in the 
two outer portions of the track appears 
to make this method impractical. 

Perhaps the most practical proposal 
is to make the two shutter vanes of 



polarizing material so oriented with 
respect to each other that where they 
overlap partial extinction occurs. The 
exposure ratio would again be fixed by 
the initial orientation of the planes of 
polarization. This system would be less 
wasteful of light than the other systems 
described. In this system, the light 
which exposes the outer regions of the 
track would be reduced to about 40% 
of its initial intensity, whereas in the 
first polarizing system described, it 
would be reduced to about 30% and 
in the semitransparent shutter system to 
about 25%. These figures imply that 
the optical system must be capable of 
exposing the film to a density of ap- 
proximately 2.2 with a density of 0.40 
to 0.60 in the beam, depending on which 
method is used. 

In order to determine the improve- 
ment which might be expected from 
such a system of double noise reduction, 
recordings were made to simulate the 
effect. One-thousand-cycle signals were 
recorded at 5-db decrements in level 
from full modulation to 60 db below 
full modulation. From full modulation 
to 20 db below full modulation, the 
galvanometer was held in its normal, 
unbiased position, and the entire slit 
was covered with a 0.3 neutral-density 
filter. The exposure was adjusted to 
give a density of 1.0 under these condi- 
tions. The galvanometer was then 
tilted to produce a 0.005-in. septum on 
the film, and signal levels from 20 db 
to 60 db below full modulation were 
recorded, still with the neutral-density 
filter over the entire slit. This would 
correspond to maximum noise reduction 
as normally applied to direct positive 
recording, i.e., the clear area has been 
reduced to a minimum and the exposed 
area has a uniform density of 1 .0. Then 
a duplicate of this last series of levels 
was recorded with the 0.3 neutral- 
density filter reduced in width so that 
it produced a 0.01 0-in. septum centered 
on the 0.005-in. septum produced by 
the galvanometer. By this means the 



318 



October 1951 Journal of the SMPTE Vol.57 



60 



50 



CD 


t 40 



.1 30 



20 



I 




Double noise reduction 



-10 -20 -30 -40 -50 -60 

Input, DB relative to 100% modulation 

Fig. 4. Output versus input for direct-playback recordings 
with single and double noise reduction. 



density outside the modulation was 
increased to about 2.0. 

The output level of each section was 
then measured and plotted against the 
input level to the galvanometer. The 
noise spectrum was limited to the band 
between 500 and 8000 cycles/sec by 
means of high- and low-pass filters. 
The results are shown in Figure 4. It 
is seen that an improvement of from 3 
to 4 db in signal-to-noise ratio could 
be expected from double noise reduction 
as compared to normal (single) noise 
reduction, when applied to the direct- 
playback type of variable-area record- 
ing. While this may not be a sensa- 



tional improvement, it is clear that 
where a large amount of this type of 
recording is done, the improvement 
would be worth the complication. 

Acknowledgment. The author expresses 
his gratitude to Mr. John Finkle, who made 
the recordings and collected the data 
presented here. 

References 

1. U.S. Patent 1,935,417, Lewis T. Robin- 
son, 1933. 

2. U.S. Patents 2,251,665, G. L. Dimmick, 
1941; 2,165,787, G. L. Dimmick, 1939. 

3. British Patent 546,332, Radio Corpora- 
tion of America, 1942. 



J. G. Streiffert: Noise Reduction for Direct Playback 



319 



The Compliance of Film Loops 



By GERHARD SCHWESINGER 



The analysis of film drives may require the knowledge of the compliance of 
looped film, defined as the rate by which the length of looped film changes 
with changing film pull. In some mechanical filters for the suppression of 
film flutter the compliance of film loops acts in analogy to the capacitance of 
electrical filters. However, it is known to be highly nonlinear. As no com- 
plete information has been published on this subject, theoretical relations 
are derived in such form that they can be conveniently applied by the de- 
signer to U-shaped and S-shaped film loops. The results are compared with 
an earlier published approximation. The effect of film curling is shown to be 
accountable in a simple manner. 



I 



N SOME TYPES of film drives the elastic 
properties of looped film sections are of 
considerable importance. In particu- 
lar, sound-film drives utilize these prop- 
erties to filter out transient and periodic 
disturbances which by various causes 
may be impressed upon the steady mo- 
tion of the film. An analysis of the 
filtering action then requires the knowl- 
edge of a relation between the film ten- 
sion and the amount of slack film in a 
film loop, usually referred to as the elas- 
tance or, inversely, compliance of film 
loops. This relation has been experi- 
mentally investigated by E. D. Cook 1 who 
pointed out its nonlinear character. 

The theoretical treatment of the film 
loop problem is mathematically more 
laborious than might be expected. In- 



contribution submitted on April 8, 

" (rial 
7 ort 



<& < t M i I i I I .M 1 IM M I ,M H M I J I I I ' 1 I Ml . \i;i If 

1951, by Gerhard Schwesinger of the Sigr 
Corps Engineering Laboratories (F< 



Monmouth, N.J.), 617 Prospect Ave., 
r, NJ. 



Little Silver, 



herently it is a matter of analytical me- 
chanics rather than motion picture engi- 
neering and this may explain why so far 
no complete information on this subject 
has been published for motion picture 
purposes. An earlier theoretical treat- 
ment is due to W. J. Albersheim and D. 
MacKenzie 2 who derived the first two 
terms of a series expansion for the film 
slack as measured between the inflection 
point of an S-shaped loop and one of the 
drums over which the film is wound. 
For practical application it is desired to 
know the total length of slack film at a 
certain film tension in the loop. This in- 
formation is not explicitly contained in 
the quoted paper. The reader might try 
to derive it therefrom by generalization, 
but he remains in uncertainty as to the 
validity of the result. In fact, there is 
no simple additive relation between (a) 
the total slack and (b) the partial 
amounts of slack as measured from the 
inflection point of the S-loop to the first 



320 



October 1951 Journal of the SMPTE Vol. 57 



Drum 2 ' 




Fig. 1. Quantities entering the analysis of the loop curve. 



and second drum, respectively. The 
earlier investigation 2 is based upon the 
simplifying assumption of a constant 
longitudinal tension along the whole 
loop. This assumption is only approxi- 
mately true and, consequently, furnishes 
results of limited validity. In order to 
establish these limits and to complete the 
earlier results, the problem of film loop 
elastance will now be treated in a differ- 
ent way eliminating any arbitrary assump- 
tions. The analysis will be extended on 
U-shaped loops which, having no in- 
flection point, are not covered by the 
paper.* 

While the exact solution of the loop 
problem can be derived in terms of ellip- 
tic integrals without much labor, it takes 
considerable mathematical reasoning to 
arrive at the first one or two members of a 
series expansion which alone is suitable 
for practical use. Unfortunately, we must 
say, the exact solution does not lend it- 
self to quick numerical evaluation. It 
will be included here, however, for com- 
pleteness and as basis of a simple approxi- 
mation to be derived from it. 

Figure 1 shows the two drums (1 and 
2) around which the film is looped. The 
quantities related to one of these drums 
carry the subindex 1 or 2, respectively. 



The longitudinal forces acting on the 
film in the contact points CP\ and CP t 
are T\ and 7~ 2 , respectively. Likewise, 
the transversal forces are denoted by R\ 
and R%. For reasons of equilibrium the 
resultants of the longitudinal and trans- 
versal forces in each contact point must 
be equal as indicated by the equally long 
film pull vectors P. The bending mo- 
ments in the contact points are MI and 
M 2 . If El is the bending stiffness of the 
film, i.e., the product of the modulus of 
elasticity E and the moment of inertia / 
of the cross section through the film, then 



EI 



The difference between the moments MI 
and MZ is balanced by an additional mo- 
ment arising from the parallel displace- 
ment of the opposing force vectors P 
relative to each other. The center of 
drum 1 is now chosen as origin of a coor- 
dinate system whose x-axis points oppo- 
site to the direction of the film pull P in 
the contact point C/V If the center co- 
ordinates of the drum 2 are called a and 
b, and the distance between the drum 
centers d, then 

a 2 + p = ^ (2 ) 



Gerhard Schwe singer: Compliance of Film Loops 



321 



Denoting the slope angle of the film loop 
with respect to the positive *-axis by e, 
and setting 



1 - 



-vs 



(3) 



one obtains the following differential 
equation of the loop curve 



dx* 



, ^ , 

^ -f + ri cos ei 



(4) 

where ^4 is a constant parameter. The 
solution of Eq. (4) can be expressed in 
terms of the tabulated elliptic integrals 
of the first kind, F(k,<p), and second 
kind, (*,*>)* (see Ref. 3). For brief- 
ness, the following notation will be used 



= F(k, a ) - 
= E(k,a) - 



If p is the radius of loop curvature and 
s n the length of the film loop between the 
contact points CA and CP 2 , one can write 
the solution as follows. 

For the U-loop: 



y = ri cos ei A* 
a = ri sin ei r 2 sin 



b = r\ cos ei -f- r<i cos e 2 



(5U) 
(6U) 

(7U) 

(8U) 
(9U) 



* E is the adopted standard notation for 
the elliptic integral of the second kind and 
also for the modulus of elasticity. Con- 
fusion will be avoided if it is kept in mind 
that the latter only occurs in the product 
EI, but never isolated. 



sin <f> 




(10U) 



(11U) 



= nsin ei + A[F - 2E]^ 


(5S) 


= r\ cos ei A 2 [ ) 
Vi P/ 


(6S) 


= ri sin ei -f- r 2 sin e 2 + A [F 1 


'< E \l\ 
(7S) 


, 9 /l 

= r\ cos e, r 2 cos e 2 A 2 [ - 
Vi 


+ 'l) 
(8S) 


- ^i;; 


(9S) 


= 4^2 + cos 2 * 1 ;*' 2 = 1- * 2 


(10S) 


^ ^ 
= ~ ; cos <pi ==- ; cos ^> 2 = 
Zp 2rj 


^ 

(us) 



It is seen that the coordinates x and y 
of the loop curve are expressed by para- 
metric equations with the parameters 
<f>, p, respectively, the former appearing 
as argument of elliptic integrals. By 
means of the Eq. (11U) or (IIS) one of 
these parameters can be eliminated. It 
is further seen that the relations are not 
identical for the two loop forms, which 
means that further investigations must be 
carried out separately. There is one 
expression, however, which is found in- 
variant in both loop shapes, namely 

. A 2 A 2 

cos e + = cos ei + 

2p 2 2n 2 

= cos 6 2 + 2~ 2 = const. (12) 

The numerical evaluation of the fore- 
going equations is easy only if both com- 
ponents 7* and R of the film pull vector 
P are known in one of the contact points, 
say, C/V In this case one knows the 
angle ^ and, from Eq. (12), also c 2 - The 



322 



October 1951 Journal of the SMPTE Vol.57 



modulus k of the elliptic integrals can be 
calculated and the integrals themselves 
taken from tables, yielding the length of 
looped film, s\ 2 , and the coordinates of 
the loop curve. Unfortunately, how- 
ever, it is by far not so easy to apply the 
above given results to the problem of film 
elastance as it occurs in sound-film drives. 
It should be recalled that in such drives 
the lateral force component R is usually 
unknown and of no particular interest 
for the designer because this component 
does not perform work during the steady 
motion of the film. Thus neither ei nor 
e 2 is known and there is no basis other 
than a guess of i or e 2 for beginning nu- 
merical calculations. In general, the 
distance d between the drums is fixed and 
the length j ]2 of the film loop is to be de- 
termined in relation to the longitudinal 
force component Ti. Mathematically 
speaking, this would require first to solve 
for i the four equations, (2), (7), (8), and 
(12), containing the four unknown quan- 
tities a, b, !, and 2 , and, second, to sub- 
stitute the result in Eq. (9), yielding the 
wanted length J J2 . Due to the transcen- 
dental character of these equations an 
analytical solution is impossible. The 
numerical solution, on the other hand, 
becomes very tedious as it essentially 
amounts to a trial-and-error procedure. 

The next step to be taken toward a 
simplified evaluation is a series expan- 
sion of the unwieldy solution given above. 
Since no arbitrary assumptions are neces- 
sary to do this, the accuracy of the result 
can be as high as desired, depending only 
on the number of series terms. 

First, it should be noted that for given 
values of the bending stiffness EI, drum 
radii r\ and r 2 , and center distance d, 
the modulus k becomes a function of only 
one remaining independent variable. 
As such one can choose the film pull P 
or one of its components, either at the 
contact point CP\ or CP 2 . One can also 
choose the parameter A or one of the 
angles i and e 2 . The preferable choice is 
A because then the mathematical rela- 
tions become symmetrical with respect to 



the drum indexes 1 and 2. Further- 
more, for motion picture film of in- 
herently low bending stiffness the param- 
eter A which has the dimension of a 
length is small as compared to the length 
.y 12 of the loops found in film drives. 
Small values of A/s iZ ensure a sufficiently 
rapid convergence of the series and per- 
mit one to establish explicitly, in a simple 
form, the relationship between k and A, 
or k' and A, which otherwise is too com- 
plex for an explicit solution. 

If the loop becomes flatter as A de- 
creases, i also decreases so that, with re- 
gard to Eq. (10U) or (10S), k tends to 
one, k' to zero, and the quantities ?i and 
<? 2 , according to Eq. (11 U) or (IIS), to 
7T/2. There exist simple approximations 
of the elliptic integrals in the vicinity of 
k = 1, <p = 7T/2, at which point they 
exhibit singularities. It can be shown 
that in this region 



F(k,<p) = In 



k sin 



+ 



., and 



cos^ <f> 



k sin *> + F(k,<p) (13) 



provided that 



(13a) 



Using the approximation (13) for 
F(k, <p) in connection with Eq. (11U) and 
(US), one can calculate the length s n of 
the loop. One finds: 



For the U-loop: 



For the S-loop: 



- k'* In 



A* 



(14U) 



A\n 



4V &'* 



,4 2 /4r 2 2 ) 



(14S) 



If A and k' tend to zero, i.e., if the film is 
pulled taut between the drums, the 
length of the flat loop becomes s t as it 
appears from Figs. 2 and 3. In order to 
furnish this limit value, from (14U) and 
(14S), k' must satisfy the condition 



Gerhard Schwesinger: Compliance of Film Loops 



323 




Fig. 2. Geometrical relations for calculating the slack in a U-loop. 

tains expressions for s iz which, substi- 
tuted in Eq. (17U) and (17S), respec- 
tively, furnish: 



It is seen that k' tends infinitely faster to 
zero than A. Therefore in all later ex- 
pansions terms in k' are negligible as 
compared to terms in A with the excep- 
tion of the term 



For the U-loop: 

5 -TTl 

2Ak 



- b* - s t + (r 2 - 



which is not always negligible because 
[F] 51 tends to oo . Applying the relation 
(15) to the approximation (13) for 
E(k ) (f>), one obtains identically for both 
loop shapes 



Apart from negligibly small terms of the 
order k' 4 the last equation is equivalent to 



- b* - St + (r, - n)7 
- 2AM + net - s 



+ \M + .... (16) 

From Figs. 2 and 3 one can read the 
length S of slack film in the loop as fol- 
lows: 



For the S-loop: 

S - 



U-loop: 

S = s u s t 

S-loop: 

S = j, 2 - s t - f 



7) r 2 (e 2 - 7) 
(17U) 

7) - r 2 (-c2 + 7) 
(17S) 



Eliminating [F]JJ and a from the sets 
of Eqs. (2), (7U), and (9U), and Eqs. 
(2), (7S), and (9S), respectively, one ob- 



- s t - (r, + r 2 ) 7 
n( l - sin Cl ) 
+ r 2 (2 - sin 2) (18S) 



Eqs. (8U) and (8S), for the center ordi- 
nate b, can be transformed so that b 
appears as function of A. One has only 
to remove ei and e 2 by aid of Eqs. (10) and 
(12). Since in flat loops k' 2 is a negli- 
gibly small quantity, the following for- 
mula holds 



324 



October 1951 Journal of the SMPTE Vol.57 




Fig. 3. Geometrical relations for calculating the slack in an S-loop. 



The upper sign is to be taken for U-loops, 
the lower sign for S-loops. From Figs. 2 
and 3 the length s t and the angle y are 
obtained as follows. 



Jt 

sin 7 



~ ri =F 



(20) 



-. (21) 



U-loop: 
S-loop: 



r\ and r% positive, so that 
rir z > 



r\ positive, r^ negative, so that 
rir z < 



The final result is 



Again the upper sign holds for the U- 
loop, the lower sign for the S-loop. The 
expression for sin y can be expanded in 
powers of A after substituting b from Eq. 
(19). Then the resulting series for sin y 
can be converted into a series for y. 
Further, the difference (i sin ei) can 
be expanded in powers of sin 2 (^ei) and 
therefrom expressed in terms of A by 
means of (10). The same procedure can 
be applied to the difference (*2 ~~ sin e^). 
Thus finally, after substituting in the two 
equations (18) all the expanded terms 
discussed above, a series expansion of the 
film slack S in terms of A emerges. It 
can be written identically for both loop 
shapes if a new sign convention is adopted 
for the two drum radii. While so far 
these radii were treated as positive quan- 
tities, the following sign rule may now 
be introduced. 



(22) 

It is seen that this series is not a true 
power series in A because exponential 
expressions appear in it. The latter are 
due to singularities of the elliptic integ- 
rals at that point k = 1, <p = IT/ 2, around 
which the series expansion for S was re- 
quired. Whether the exponential term 
is negligible in comparison to the highest 
power term given above must be decided 
in the particular practical application. 
Presumably in most motion picture appli- 
cations it will be negligible. The case 
that the magnitude of the exponential 
term approaches that of the lower power 
terms may be considered as an indication 



Gerhard Schwe singer: Compliance of Film Loops 



325 



that the film loop is not flat enough for 
the limited number of series members in 
Eq. (22). 

In order to establish a basis for the 
comparison of the above result with the 
earlier published paper, 2 the special case 
now is considered that the film slack S 
is to be measured between drum 1 and 
the inflection point of an S-loop. 
As the radius of curvature at the inflec- 
tion point is infinite, one might try to 
derive the just mentioned special case 
from Eq. (22) by making r 2 infinite. 
However, according to Eq. (US), cos ^ 2 
would then equal zero and thus violate 
the condition (13a). It is therefore nec- 
essary to go back to the initial equa- 
tions and to apply there the substitution 
r 2 = oo. It can be shown that also for 
infinite values of r 2 the correct result is 
obtained from the series (22), if the 
vanishing exponential term is replaced 
by another exponential term, namely 

2s t 



Comparing now this result with Eq. 
(67) of Ref. 2, one finds that the latter 
does not contain exponential members. 
The reason is that the "loop equation 
(60)" of Ref. 2 is only an approximation. 
The first series term of the quoted Eq. 
(67) is correct, the second term is ap- 
proximately correct as the "inflection 
distance Z)" of Ref. 2 is approximately 
equal to s t . It further appears that no 
general simple additive rule exists be- 
tween the total slack S and the partial 
amounts S\ and S& measured from the in- 
flection point to the two drums. Only 
with regard to the first approximation, 



(23) 



does such an additive rule exist. It is 
remarkable that, in first approximation, 
S is independent of the drum separation 
d. 

In order to obtain from Eq. (22) the 
length S, the film pull P must be known. 
As pointed out earlier, the designer of 



film drives is primarily concerned with 
the tangential component 7" of the film 
pull P because only this force 7" reflects 
in the torque JV exerted on the drums. 
As it is seen from Fig. 1, the torque MI 
on drum 1, counted counterclockwise, is 

Ai = Mi + Tin = ^ + Tin. (24) 
Using the parameter 




one can convert the series (22) into an- 
other series expanded in terms of t\ so 
that, in conjunction with Eq. (25), for 
any torque N\ the length S can be directly 
determined. The converted series readr, 

?.*!/! L\ _tf/l-iY 

12 W "*" r 2 2 / 8s t \ ri rj 
20 



(26) 



The coefficients of the first two series 
members are the same as those of the 
first two members of series (22) . Thus as 
first approximation the simple formula 
(23) is valid again if the tangential force 
T is substituted for the film pull P. 

Until now the film was treated as a 
homogeneous flexible rod which in the 
absence of external forces is perfectly 
straight. As to homogeneity, it must be 
said that the perforation holes cause a 
periodic variation of the bending stiff- 
ness, resulting in a loop curve which is 
slightly wavy. This variation, however, 
is very small and presumably of no im- 
portance with regard to the amount S of 
looped film, especially if a suitable aver- 
age value is assumed for the bending stiff- 
ness. On the other hand, film curling, 
the second offender, may sometimes pro- 
duce an appreciable effect. As far as 
longitudinal film curling is concerned, 
this effect can be taken into account in 
the theoretical relations derived above. 



326 



October 1951 Journal of the SMPTE Vol. 57 



Suppose the natural radius of curvature 
of the curling film in the longitudinal di- 
rection is constant for the considered 
length of film and denoted by r n , counted 
positive if the film tends to curl around 
drum 1. Since in this case the first of 
the two Eqs. (1) modifies to 



El I- - - 



M l 



the relation (25) for the parameter t v 
changes to 



(27) 



The loop Eq. (4) remains unchanged. 
This can be visualized from its physical 
meaning, namely, being an equilibrium 
condition for the moments acting on the 
film. If a piece of film is considered be- 
tween the contact point CPi and any 
other point of the loop, it is seen that the 
two opposing bending moments at the 
ends of this piece are proportional to the 
change of curvature which the film has 
undergone when being deformed from its 
natural state. The difference between 
these two bending moments is balanced 



by a force couple which originates from 
the relative parallel shift of the opposing 
force vectors P at the considered points 
(see Fig. 1). Since only the difference 
between the two bending moments enters 
the equilibrium condition, one need con- 
sider only the difference of the changes 
of curvature at the two points. But in 
this difference the original curvature of 
the curled film drops out as it was as- 
sumed constant over the whole length of 
film. Thus the loop Eq. (4) and all en- 
suing relations, including the final result 
(26), are independent of r n . In other 
words, the effect of film curling reflects 
only in the value of the parameter ti as 
per Eq. (27). This value in connection 
with Eq. (26) yields the correct length of 
slack film. 

References 

1. E. D. Cook, "The technical aspects of 
the high-fidelity reproducer," Jour. 
SMPE, vol. 25, pp. 289-313, Oct. 1935. 

2. W. J. Albersheim and D. MacKenzie, 
"Analysis of sound-film drives," Jour. 
SMPE, vol. 37, pp. 452-479, Nov. 1941. 

3. E. Jahnke and F. Emde, Tables of Func- 
tions with Formulae and Curves, Dover 
Publications, New York, Reprint 1945. 



Gerhard Schwesinger: Compliance of Film Loops 



327 



Auditory Perspective A Study of the Biologi- 
cal Factors Related to Directional Hearing 



By H. G. KOBRAK 



The biological principles of auditory localization as related to stereosound 
reproduction are discussed. The human head carries two laterally-attached, 
biological sound receivers and the conduction of sound within these receivers, 
their position and the role of the skull in the sound field are also discussed. 
The attributes of the acoustic signal relevant to sound localization and the 
role of the central nervous system in the integration of binaural auditory 
stimulation are described. The factors of experience and training are stressed. 



AN PRIMITIVE LIFE, the sense organ of 
hearing has to fulfill two basic functions. 
It has to warn the individual of approach- 
ing danger and must enable him to seek 
and to find the mate. In coping with the 
function as warning mechanism, it is 
absolutely essential that the individual 
not only be notified that a dangerous 
sound has occurred, but it is equally im- 
portant that the direction from which 
the danger lurks be known simultane- 
ously. The ability of directional hearing 
must therefore be considered a basic and 
important function of the ear. 

All attempts to explain the directional 
abilities of the human ear assume that 
the hearing organ receives stimuli which 
vary with the position and distance of the 
source. The interpretation of certain 
physical cues, based on past experience, 
is the quintescence of directional hearing. 



Presented on May 3, 1951, at the Society's 
Convention in New York, by Dr. H. G. 
Kobrak, Division of Otolaryngology, Uni- 
versity of Chicago, 950 E. 59th St., 
Chicago, 111. 



The interpretation must give information 
on the distance of the sound source and 
its direction. In the presence of several 
sound sources, a spatial orientation in re- 
gard to the relative position of each 
source is accomplished. This spatial 
perception of different sound sources is 
called auditory perspective. 

Attempts have been made to create an 
auditory perspective in an audience. 
The sensation of three-dimensionality of 
the sound in the listener has been called 
the stereophonic effect. It is natural 
that all experiments attempting the crea- 
tion of stereophonic effects must be based 
on a thorough knowledge of auditory per- 
spective. 

Auditory perspective is based on, and 
accomplished by, a number of factors. 

1. Physical factors, concerning the 
attributes of the acoustic signal. 

2. Physiological factors, concerning 
the biological characteristics of the hu- 
man ear as sound receiver. 

3. Psychological factors concerning 
the interpretation of acoustic cues. 



328 



October 1951 Journal of the SMPTE Vol. 57 



4. Coordination with the information 
received by other sense organs. 

If a sound comes from the side, as dis- 
tinguished, say, by sight, most likely a 
short turn of the head will be made in 
order to face the sound source. The 
movement of the neck muscles as pro- 
prioceptive stimulus and the visual clue 
are combined and utilized in the spatial 
auditory perception. Among the psy- 
chological factors there is a most impor- 
tant one which is responsible for the 
creation of the stereophonic effect: 
the acoustic experience of the audience. 

The individual will unknowingly com- 
pare his present auditory cues with simi- 
lar past experiences. 

How important experience is will be 
illustrated in Fig. 1. It is an example 
taken from stereovision, but it applies 
also to acoustic stereoperception. 

Figure 1 shows three forms of plane 
geometry: a square and two rhomboids. 
Undoubtedly they are two-dimensional 
entities. If the three planes are put to- 
gether in a certain way, most observers 
will perceive a three-dimensional entity, 
namely a cube. A person who never 
before saw a cube would not obtain the 
stereoeffect. Furthermore, it should be 
recognized that Fig. 1 gives not one, but 
two possible three-dimensional solutions. 
The sketch can represent a cube and also 
a half-open box with the left and lower 
sides missing. The vertical square, in 
such a case, appears to be farther away 
from the eye, while the two rhomboids 
appear to come toward the eye. The 
sketch was actually drawn for this stereo- 
effect. Observers visualize according to 
their experience. A cube is frequently 
encountered, while the other form would 
be rarely observed. Therefore, the ma- 
jority will see a cube in Fig. 1. 

Another comparison with the sense of 
vision seems in order. Stereovision is 
accomplished by the coordination and 
the integration of the perception of the 
two eyes. The mechanism by which the 
eye is able to render three-dimensional 
perception is considered well known. 



Fig. 1. The role of experience and 
probability in stereoperception. 

The upper part of this sketch shows a 
square and two rhomboids. By placing 
these two-dimensional forms together, a 
stereoperception results. Most observers 
will see in the lower sketch a cube; a second 
stereoeffect (square away from eye) will be 
seen less frequently because a cube is an 
object which is more frequently encoun- 
tered. 



Since light travels in a straight line, the 
angle which the eyeball has to assume in 
order to face the source gives a clear defi- 
nition of the direction. Since there will 
be a small difference in the angles which 
the right eye assumes, compared to those 
of the left eye, we have a simple geo- 
metrical problem: a base line of known 
dimension, i.e., the interpupillary dis- 
tance and two angles. Elementary trig- 
onometry will permit us to give direction 
and estimation of distance. (An impor- 
tant factor in distance estimation is 
familiarity with the objects. The size of 
the object should be known.) 

The problems of auditory perspective 
are considerably more complicated be- 
cause of the nature of the sound stimulus. 
Sound does not travel in a straight line 
nor does it produce sharp shadows. At 
least, this is true for the lower frequencies. 

It must be assumed, therefore, that a 
simple trigonometric approach, as in 
stereovision, cannot solve the problems of 
auditory perspective. Some animals, 
however, utilize the position of the outer 



H. G. Kobrak: Auditory Perspective 



329 




Fig. 2. The human ear. Phase relation of the two cochlear windows. 

Enlarged picture of the cochlea: the stirrup, st, the round window, rw, the promontory, 
P, and the facial nerve, F. Under normal conditions, the stirrup executes acoustic vibra- 
tions which in turn produce vibrations of the fluid column in the scalae vestibuli, sv, the 
basilar membrane and the scala tympani, s tym. The round window membrane acts as 
a "yielding area." Its phase is opposite to that of the stirrup. This normal phase rela- 
tion is essential for normal directional hearing. 

In patients with destroyed sound conduction system, sound impinges onto the two 
cochlear windows directly and the phase of the two windows is identical. Disturbance 
of directional hearing results. 



ear for directional hearing much as the 
eyes are utilized in turning toward the 
visual source. 

Some game animals have large outer 
ears which are movable in all directions. 
The larger size and the directional quali- 
ties of the pinna in these animals give a 
greater hearing sensitivity for faint sounds 
and better directional selectivity. It has 
been estimated that the ear of the deer is 
superior to that of the hunter by 8 db in 
hearing faint sounds. 1 In higher-order 
animals like apes, and also in man, the 
motility of the outer ear is no longer 
found. With the assumption of the up- 



right position for locomotion and im- 
proved eye and brain function, there is 
apparently a shift to assign to the eyes 
and to the brain a greater part of the 
judgment of directional hearing. The 
superior development of the brain per- 
mits a more critical and correct inter- 
pretation of the acoustic environment. 

When we study the auditory perspec- 
tive today, we should not overlook this 
development within the animal kingdom. 
It shows that nature has not intended the 
ear to be the only judge in directional 
hearing. It is a coordinated interpre- 
tation of acoustic stimulation in conjunc- 



330 



October 1951 Journal of the SMPTE Vol.57 



tion with impressions obtained from 
other sense organs and integrated and 
judged by the centers of the central ner- 
vous system. 

The human ear is a biological trans- 
ducer which changes mechanical waves 
into nerve impulses. Naturally, any 
bodily structure which possesses mass and 
stiffness will execute forced vibrations 
under the influence of the acoustic signal. 
When sound impinges onto the ear, a 
number of middle and inner ear struc- 
tures begin to oscillate as forced vibra- 
tions. However, some structures possess 
an especially favorable construction and, 
therefore, are more effective and eco- 
nomical in the conduction of sound 
energy. Experimental evidence has 
shown that the eardrum, with the three 
attached bones (hammer, anvil and 
stirrup), is the best and, therefore, most 
important sound conductor, while con- 
duction through the bone of the skull and 
through the air of the middle ear is in- 
significant under normal conditions. 

The normal process of sound conduc- 
tion through the chain of small bones in 
the middle ear to the oval window of the 
cochlea is fundamentally an impedance- 
matching arrangement. The elastic 
medium in which man lives and through 
which the acoustic signals arrive is air. 
The inner ear is filled with fluid. The 
ossicular chain is an impedance-matching 
device which bridges the air-water bound- 
ary. The footplate of the stirrup, by 
its acoustic oscillations, sets the fluid of 
the inner ear into vibrations. It is a bio- 
logical underwater sound source. The 
vibrating fluid volumes must be con- 
sidered as mass displacements. The 
round window membrane (Fig. 2) con- 
stitutes a yielding spot. When the stir- 
rup pushes inward, the round window 
membrane moves outward. On the 
other hand, when the stapes executes an 
outward motion, the round window 
moves inwardly. 

An experimental method was worked 
out at the University of Chicago by which 
it was possible to visualize and to photo- 



graph these vibrations within the ear 
under controlled experimental con- 
ditions. [As a part of the Convention 
presentation a motion picture was shown 
by which the oscillations of the stirrup 
and the round window membrane were 
seen and the phase relation observed.] 
This normal phase relation is important 
for directional hearing. Bekesy 2 has 
carried out interesting experiments 
on persons with diseased ears. Patients 
who have lost the eardrum and hammer 
and anvil, either by disease or by oper- 
ation, have a different phase relation 
between oval and round window. In 
these cases the predominance of ossicu- 
lar sound conduction is missing. Sound 
waves enter the middle ear and impinge 
on both windows with practically the 
same phase. Experiments show that 
these patients judge the direction of a 
sound source opposite to that of a person 
with normal hearing. In cases of ear- 
drum perforations, an artificial eardrum 
can be inserted which occludes the direct 
access of sound waves to the middle ear 
cavity. The directional hearing then 
changes again to normalcy. [The thera- 
peutic procedure of the surgeon which 
brings about this reversal of directional 
hearing was also demonstrated by a 
motion picture.] 

When sound impinges onto the head of 
an observer, a certain percentage of the 
total sound energy will be conducted 
through the bones of the skull. This 
pathway of sound leads directly to the 
inner ear without utilizing the chain of 
middle ear ossicles (Fig. 3). The otic 
capsule undergoes periodic contractions 
and rarefactions which produce vibra- 
tions in the inner ear fluids. The oscil- 
lations of the introcochlear fluid produce 
a hearing sensation which is identical to 
that produced by sound conduction 
through the ossicles. There is, however, 
one important difference. The direct 
bone conduction is a conveyance through 
a solid medium, therefore, a fast phenom- 
enon. The sound conduction through 
eardrum and ossicular chain is measur- 



H. G. Kobrak: Auditory Perspective 



331 




Fig. 3. The human ear; concept of bone conduction; a cross section of the middle 

ear, M, and the cochlea, C. 

The two bony canals (scalae) which are winding in 2% coils around the axis are shown. 
During the process of hearing, some sound energy travels through the bone and produces 
waves of compressions and rarefactions of the bony capsule. This is called bone conduc- 
tion (indicated by single arrows). Normally, there is a phase difference between bone- 
conducted sound and ossicular sound conduction. However, the influence of direct bone 
conduction is small in normal ears. The impulses set up in the nerve are carried through 
the nerve fibers in the axis of the cochlea (double arrow) and go into the central nervous 
system through the acoustic nerve (triple arrow). 



ably slower. * Therefore, under normal 
conditions there is a phase difference be- 
tween the direct bone conduction and the 
ossicular sound conduction. This phase 
difference has been demonstrated experi- 
mentally by Krainz. 3 Normally, the 
percentage of sound energy traveling 
through the skull bones to the inner 
ear is negligible compared to the con- 
duction through the middle ear chain. 4 



* The time element in ossicular sound con- 
duction can be demonstrated in motion 
picture records. 



However, a person wearing a hearing 
aid utilizes direct tissue-and-bone con- 
duction to an appreciable extent. The 
phase difference between the two stimuli 
may be important enough to produce dis- 
turbance of the auditory perspective. 
Due to the fact, however, that man uti- 
lizes his past experience and his visual and 
tactile cues to such a large extent, this 
disturbance is easily checked and 
counterbalanced. 

For natural and correct judgment of 
sound location both ears are necessary. 
The destruction of one ear creates errors 



332 



October 1951 Journal of the SMPTE Vol. 57 



in the judgment of sound direction. 
This can be demonstrated easily and has 
been known for a long time. 

If one plugs an ear with cotton, appar- 
ent direction of the sound source may 
differ considerably from the true one. 
The number of persons suffering from 
various degrees of hearing impairment is 
great. It is very difficult to give exact 
figures: 1,500,000 to 3,000,000 children 
in the United States are estimated to 
suffer from defective hearing. Exten- 
sive surveys among adults, comparable to 
those of school children, are more diffi- 
cult to make. One can say that roughly 
5% of the future adult citizens of the na- 
tion have hearing losses. 

Several factors of binaural hearing 
have been investigated as to their impor- 
tance in sound localization. 

There are several principal ways in 
which the sound signal reaching the right 
ear may differ from the sound signal inci- 
dent to the left ear. The intensity of the 
stimulus, its phase, its wave composition 
and its time of arrival may differ. 

An intensity difference, provided it is 
great enough, causes a displacement of 
localization toward the ear receiving the 
greater stimulus. This phenomenon is 
more important in high tones. The 
head is a small obstacle for low tones and 
its interference, therefore, negligible. 
However, for frequencies above 5000 
cycles/sec the difference in loudness level 
between the two ears may be great. 
Steinberg and Snow 5 measured a differ- 
ence of 30 db for 10,000 cycles/sec for an 
azimuth of 90 . The difference may be 
even greater for other azimuths. 6 When 
the sound stimulus is a complex signal, 
such as music or speech, then some of the 
high-frequency components are lost to 
the ear on the far side of the head and a 
considerable difference distortion in the 
composition of the signal results. Due 
to the shadow effect for high tones, the 
two auricles cast a definite shadow for 
tones coming from the rear. 

When two tones, differing in phase, are 
conducted to the ears, the listener will 




1000 cpt 




1116 kc 



Fig. 4. The physical properties of the 
skull and its importance on directional 
hearing. Human skull seen from above. 

The sketch tries to demonstrate the size 
of the average human head in relation to 
the wavelength for airborne tones of 1000 
cycle/sec and 16,000 cycle/sec. It is ap- 
parent from this sketch that low tones have 
a wavelength which is large in comparison 
to the skull. The diameter of the head 
equals roughly one-half of the wavelength 
of 800 cycle/sec. High frequencies above 
5000 are perceived best when entering from 
an angle 30 forward. This is due to the 
shape and position of the auricle. 

The velocity of sound in air being 330 
m/sec, it takes 0.0006 sec for the sound to 
travel a distance equal to the diameter of 
the head. This is the maximum time differ- 
ence which can occur when a single sound 
falls on the ears. 

localize the sound source toward the side 
of the leading phase. A sound wave 
coming from the side will reach the closer 
ear before it reaches the ear on the far 
side of the head. It can readily be seen 
(Fig. 4) that a situation may arise in 
which the difference in the length of the 
path between the two ears is greater than 
half of the wavelength of sound. Under 
such a condition, the location of the 
sound source on either side of the head 
may give the same phase difference at the 
two ears. Therefore, for high frequen- 
cies, localization based on phase differ- 
ences becomes unreliable. The critical 
frequency is about 800. The wavelength 
of 800 cycle/sec in air is about 40 cm, 



H. G. Kobrak: Auditory Perspective 



333 



which is twice the distance between the 
ears. 

If the ears are stimulated by brief 
clicks with one click delivered a little 
earlier than the other, a single click is 
heard and localized on the side of the 
first click. Small time differences are 
effective. Hornbostel and Wertheimer 
found 30 yusec as threshold. If the time 
difference is increased, the apparent lat- 
eral displacement of the sound is in- 
creased until critical value is reached at 
630 /tsec. If the time of incidence differs 
more than this value, two distinct tones 
are heard, one on one side and one on the 
other. If a source of a continuous sound 
is near the head of an observer, the ampli- 
tude of the signal at the near ear is greater 
than that of the far ear. Apparently it 
is possible for the ear to utilize the ampli- 
tude ratio for estimation of the distance 
of the source. The results are rather un- 
stable for different observers. 

If a listener is permitted to move his 
head while determining the direction of 
the sound source, his ability to judge is 
greatly enhanced. Most people know 
this instinctively and move their heads 
while listening. If a sound comes from 
the front, it will appear to come from the 
right side when the head is turned to the 
left. The opposite is true when the head 
is turned to the right. The sound source 
will then appear to be on the left side. 



The importance of small head movements 
for directional sound perception can 
hardly be overemphasized. Some phy- 
siologists even go as far as to "explain" 
the juxtaposition of the cochlea and the 
vestibular organ in the inner ear by the 
coordinated body movements in relation 
to sound sources. 

For a conscious sensation of directional 
hearing, it is necessary that the central 
nervous system (Fig. 5) receive and utilize 
the small differences of stimulation be- 
tween the right and left ear. 

Stereophonic Effect 

When a listener is facing an orchestra, 
he is exposed to a complex sound stimulus 
which originates not from a pointlike 
sound source but from an area. The 
spatial relation of the various instruments 
can be sensed by the listener. In other 
words, from the influx of the various 
sounds he can pick out the direction from 
which the sound of each group of instru- 
ments comes. This is the stereophonic 
effect of multiple sources of sound. 

Important experiments on the repro- 
duction of spatial relation of multiple 
sound sources were carried out by mem- 
bers of the Bell Telephone Laboratories 
during the last 20 years. 5 

Ideally, an infinite number of micro- 
phones and loudspeakers would be 
needed to obtain perfect reproduction. 



Fig. 5. Sketch of the auditory pathways in the central 

nervous system. 

A highly simplified diagram. From the cochlea, G, 
of the inner ear an acoustic nerve, AN, leads to the 
medulla oblongata, 1. There the nerve fibers make 
contact with a new unit of the auditory system. A part 
of the fibers cross to the opposite side, the rest ascends 
to the next higher relay center located in the inferior 
collicus, .2. There another interruption and another 
crossing of some fibers take place. After another relay 

I I station in the medial geniculate body is passed, the 

fit* ^\ 1 auditory pathway reaches the auditory cortex, 3. 
& -^fc-----^/ The diagram demonstrates the anatomical locations 

-+ A Nl where impulses from one ear are partially transmitted to 

v, the opposite. The interplay of messages from right and 

left ear is interpreted by the high acoustic nerve centers 

and integrated into an auditory perspective. There are at least three levels known ( 1 , 2, 3) 
within the central nervous system where impulses cross to the opposite side. 




334 



October 1951 Journal of the SMPTE Vol. 57 



Experiments have shown, however, that 
only three, perhaps even only two micro- 
phone-loudspeaker combinations will 
give satisfactory auditory perspective. 
In the experiments of Steinberg and 
Snow, microphones were set on the stage 
and the corresponding loudspeakers were 
placed before an audience. The loud- 
speakers were placed behind a curtain. 
A group of observers were asked to judge 
from which point behind the curtain the 
signals appeared to originate. With 
three-channel reproduction, there was a 
good correspondence between the caller's 
actual position on the pickup stage and 
his apparent position on the virtual stage. 
Both attributes of forward and back as 
well as right and left differences were 
fairly well identified. 

When the three-channel reproduction 
was reduced to a two-channel reproduc- 
tion, the observers reported that the 
stage appeared less deep, but perhaps 
broader. Steinberg and Snow con- 
cluded that the loudness difference at the 
two ears of the observer is responsible for 
the accurate judgment of the angular 
localization. 

Conclusions 

The engineer who attempts to create 
auditory perspective in an audience 
should have in mind the auditory experi- 
ence of his audience. If we interpret the 
facts of comparative physiology cor- 
rectly, we come to the conclusion that 
the development in the animal kingdom 
led from a large mobile directional sound 
receiver (as found in fleeing herbivores) 
to a smaller and immobile, perhaps even 
rudimentary, pinna of the primates and 
man. Parallel to this transformation 
of the outer ear there is the assumption of 
erect posture and improvement of brain 
function. This means that man uses 
visual clues to a considerable extent. In 
addition, the brain will act to interpret 
the signals by integrating the auditory 
messages and comparing them with non- 
aural stimuli. Previous experience will 



facilitate the creation of a three-dimen- 
sional aspect. If there is a dog in the 
corner of the room and some barking is 
being heard from this direction, most 
listeners will combine the visual and 
auditory impression, but if there is some 
meowing coming from the dog's mouth, 
the alert listener will search around for 
another sound source, because his experi- 
ence tells him that the meow could not 
have come from the dog's mouth. 

Movements of the head are very impor- 
tant for directional hearing. Most 
people will make small turns of the head 
unknowingly while listening to a hidden 
sound source. If the sound source is 
visible, the listener will turn his head 
until he faces the sound source. 

Normal hearing ability in both ears is 
the prerequisite for natural auditory per- 
spective. One-sided deafness produces 
errors of sound localization. The num- 
ber of persons suffering from various de- 
grees of hearing impairment is great. 
However, since man utilizes visual per- 
ception to a great extent, aural defi- 
ciencies can, in most cases, be overcome 
without resulting in any serious auditory 
disorientation. 

References 

1. L. A. Watson and T. Tolan, Hearing 
Tests and Hearing Instruments, William & 
Wilkins, Baltimore, 1949. Page 10. 

2. Georg v. Bekesy, "Zur Physik des 
Mittelohres Und uber das Horen bei 
fehler-haftem Trommelfell," Akust. Z., 
vol. 1, p. 13, 1936. 

3. W. Krainz, "Das Knochenleitungs- 
problem," Z. Hals-Nasen-Ohrenheilkd., 
vol. 15, p. 306, 1926. 

4. E. Barany, "A contribution to the 
physiology of bone conduction," Acta 
Oto-Laryngol., Supplement 26, p. 1, 1938. 

5. J. C. Steinberg and W. B. Snow, "Sym- 
posium on wire transmission of sym- 
phonic music and its reproduction in 
auditory perspective," Bell System Tech. 
J., vol. 13, p. 245, 1934. 

6. L. J. Sivian and S. D. White, "On 
minimum audible sound fields," /. 
Acoust. Soc. Am., vol. 4, p. 288, 1933. 



H. G. Kobrak: Auditory Perspective 



335 



Color Television -U.S. A. Standard 



By P. C. GOLDMARK, J. W. CHRISTENSEN and J. J. REEVES 



This paper is divided into four sections. The first deals with the actual 
standards as established by the Federal Communications Commission and 
discusses their colorimetric significance. Section II discusses the design and 
performance of typical commercial color-television receivers. Section III 
will be of special interest to the broadcaster as it describes the conversion 
of existing black-and-white studio equipment for color-television use. Some 
data on studio installation and lighting are also supplied. Section IV deals 
with nonbroadcast uses of color television and describes industrial color- 
television equipment known as Vericolor. 



I. Color-Television Standards 



MOST OF THE fundamental data and 
early developmental stages -of the field- 
sequential color-television system have 
been available to the engineering pro- 
fession, partly from earlier publications 
(also, see the paper immediately follow- 
ing in this JOURNAL) and partly from 
material presented at the FCC hear- 
ing. 1 " 3 Now that color television has 

A contribution submitted September 4, 
1951, by Peter C. Goldmark, John W. 
Christensen and James J. Reeves, Labora- 
tories Division, Columbia Broadcasting Sys- 
tem, Inc., 485 Madison Ave., New York 
22, N.Y. This paper is being published 
simultaneously in the Proceedings of the I.R.E. 
This paper is, in parts, a development from 
the one given Oct. 16, 1950, at the Society's 
Convention at Lake Placid, N. Y. 

1 P. C. Goldmark, J. N. Dyer, E. R. Piore 
and J. M. Hollywood, "Color television 
Pt. I," Proc. I.R.E., vol. 30, pp. 162-182, 
Apr. 1942. 

2 P. C. Goldmark, E. R. Piore, J. M. 
Hollywood, T. H. Chambers and J. J. 
Reeves, "Color television Pt. II," Proc. 
I.R.E., vol. 31, pp. 465-478, Sept., 1943. 

8 P. C. Goldmark, "Brightness and con- 
trast in television," Elec. Eng., vol. 68, pp. 
237-242, Mar. 1949. 



attained the status of commercial opera- 
tion, it seems advisable to fashion this 
paper in such a way that it is most 
useful to the studio and receiving- 
equipment engineer. 

It is appropriate to begin with a 
recital of the official FCC color-television 
standards as they appeared in the 
Federal Register and to follow this with a 
brief discussion of their significance from 
a colorimetric point of view. 

It is ordered, That effective the 20th 
day of November, 1950, the Commission's 
"Standards of Good Engineering Practice 
Concerning Television Broadcast Stations" 
are amended in the following respects: 

(I) Paragraphs 5, 6, 7 and 8 of Section 
IB entitled "Visual Transmitter" are 
revised to read as follows: 

5. Color transmission. The term "color 
transmission" means the transmission of 
color television signals which can be 
reproduced with different values of hue, 
saturation and luminance. 

6. Field. The term "field" means scanning 
through the picture area once in the 
chosen scanning pattern and in a single 
color. In the line-interlaced scanning 



336 



October 1951 Journal of the SMPTE Vol. 57 



pattern of two to one, it means the scanning 
of the alternate lines of the picture area 
once in a single color. 

7. Frame. The term "frame" means 
scanning all of the picture area once in a 
single color. In the line-interlaced scan- 
ning pattern of two to one, a frame consists 
of two fields. 

8. (a). Color field. The term "color field" 
means scanning through the picture area 
once in the chosen scanning pattern and 
in each of the primary colors. In the 
line-interlaced scanning pattern of two to 
one, it means the scanning of the alternate 
lines of the picture area once in each of the 
primary colors. 

(b). Color frame. The term "color frame" 
means scanning all of the picture area 
once in each of the primary colors. In 
the line interlaced scanning pattern of two 
to one, a color frame consists of two color 
fields. 

(II) Paragraphs 5, 6 and 13 of Section 
2A entitled "Transmission Standards and 
Changes or Modifications Thereof are 
revised to read as follows: 

5. For monochrome transmission the 
number of scanning lines per frame shall 
be 525, interlaced two to one in successive 
fields. The frame frequency shall be 30, 
the field frequency 60, and the line fre- 
quency 15,750 per second. 

6. For color transmission the number of 
scanning lines per frame shall be 405, 
interlaced two to one in successive fields 
of the same color. The frame frequency 
shall be 72, the field frequency 144, the 
color frame frequency 24, the color field 
frequency 48, and the line frequency 
29,160 per second. 

13. The level at maximum luminance 
shall be 15% or less of the peak carrier level. 

(III) The foll6wing new paragraphs 19 
and 20 are added to Section 2A: 

19. The color sequence for color trans- 
mission shall be repeated in the order red, 
blue, green in successive fields. 

20. The transmitter color characteristics 
for color transmission shall be such as to 
reproduce the transmitted colors as cor- 
rectly as the state of the art will permit on a 
receiver having the following trichromatic 
coefficients, based on the standardized 



color triangle of the International Com- 
mission on Illumination : 

Red Blue Green 

x = 0.674 x = 0.122 x = 0.227 
y = 0.326 y = 0.142 y = 0.694 
(IV) New "Appendix I" attached hereto 
entitled "Television Synchronizing Wave- 
form" is substituted for "Appendix I" 
of the "Standards of Good Engineering 
Practice Concerning Television Broadcast 
Stations." 

(Sees. 4, 303, 48 Stat. 1066, as amended, 
1082 as amended; 47 U.S.C. and Sup. 
154, 303, interprets or applies Sec. 301, 
48 Stat. 1081; 47 U.S.C. 301) 
Released: October 11, 1950. 
Figure 1 shows the television syn- 
chronizing waveforms which combine 
both the black-and-white and the color 
waveshapes as well as their numerical 
values. 

Referring to paragraph 20 of the pre- 
ceding standards, dealing with the 
transmitter color characteristics, it is 
important to realize their real signifi- 
cance. The receiver primaries E to 
which the standards refer are shown in 
Fig. 2. The coordinates on the ICI 
color diagram correspond to those 
listed in paragraph 20. These primaries 
E satisfy certain performance conditions 
for specific types of color receivers. The 
ratios of the luminosities of these prim- 
aries are green to red to blue as 2.9 to 
1 .8 to 1 . Because of the favorable ratios, 
these primaries at the receiver will 
permit a high flicker threshold illumi- 
nation. Thus, if receiver illumination 
as high as 24 ft-L (foot-Lamberts) is 
required and a color disk is used, these 
primaries E are recommended. The 
theoretical maximum color gamut pos- 
sible with these primaries is more than 
adequate. 

Calculations and experiments, com- 
paring the maximum possible color 
fidelity with primaries E using only the 
major positive lobes of the transmitter 
color curves (Fig. 3), have shown that 
the color fidelity obtainable is at least 
as good as, if not better than, Koda- 
chrome. This is particularly true if 



Goldmark, Christensen and Reeves: Color Television 



337 



h 

I 

!* 



i ii ipi 'i jK fi,i %8 i M ii|ijMi|ii 

JHI??!? lii'llii. ! 

3 s 8 .S s 2 v fc 

ri ra ^ ** e ^ 

t-S 22 2 




^ 




338 



October 1951 Journal of the SMPTE Vol. 57 




^ 

u 
Is 








l/l 








V 












i 


* 


i 

j ^ 




S 


: 


p 








1 i i 




1 












i 


\ 


t 





Goldmark, Christ en sen and Reeves: Color Television 



339 



Table I. Relative Luminosity Values of Original and Reproduced Colors 



Wratten 
filter 
No. 


Filters through 
Illuminant C 
Published Actual 
values values 


Reproduced with 
Primaries Primaries 
C A 


Filters photographed 
with Kodachrome 
TypcS 
Before After 
(with (with 
3200 K) 3200 K) 


13 
22 
32 
38 


2.57 2.06 
2.54 2.10 
1. 1. 
3.12 2.39 


2.97 

2.25 
* __ 

l'.61 


2.42 
1.81 
1. 
1.43 


1.56 0.46 
2.30 1.74 
1. 1. 
1.78 0.96 



the distortion in luminosity values is 
also taken into consideration. Figure 4 
and Table I show the tabulated results. 
With the field-sequential system, when 
using a single camera, it is not practical 
to employ masking; that is, utilization of 
the negative lobes. In view of the 
results of the fidelity experiments just 
referred to, masking can be dispensed 
with. It will be shown that the standard 
transmitter primaries as used in practice, 
namely, without the negative and minor 
positive lobes, as shown in Fig. 5, can 
satisfy not only primaries E but also a 
wide variety of other receiver primaries. 
This gives the receiver manufacturer 
the necessary flexibility in the choice 
of color fidelity, resistance to flicker, 
light efficiency, etc. In Fig. 4 the color 
fidelity of another set of primaries has 
been plotted against primaries A as 
well as Kodachrome. They are re- 
ceiver primaries C and are represented 
in Fig. 6. These color primaries were 
theoretically derived by an early indus- 
trial color committee, using Wratten 
filters Nos. 47, 58 and 25 combined 
with Illuminant C (one of the ICI 
illuminants). The resultant white when 
using equal amplitudes of red, blue and 
green is again Illuminant C. Another 
set of receiver primaries is plotted in 
Fig. 6, namely, primaries D using a 
specific phosphor mixture with Wratten 
filters Nos. 47, 58 and 26. Both primaries 
D and C show better blues than primaries 
A or primaries E as illustrated in Fig. 2; 
however, the greens of primaries A and 
primaries E are superior while the reds 



of all four primaries, A, C, D and E 
are almost identical. 

The more recent primaries E differ 
only slightly from primaries A. They 
were derived from primaries A in such 
a way as to provide a more suitable 
white, using available phosphor-filter 
combinations. 

The luminosity ratios of primaries 
A, C and D are given in Fig. 6 and it 
can be seen that primaries A (similar to 
primaries ) belong to the low 
luminosity-ratio primaries (high flicker 
threshold illumination). Transmitter 
primaries for primaries A, C and D 
have been calculated and plotted with 
the condition that equal amplitudes 
will correspond to the desired white at 
the receiver. These transmitter pri- 
maries are shown in Fig. 7. Actually, 
only two families of curves are shown 
because primaries C and primaries D 
result in almost identical transmitter 
characteristics as represented by the 
broken curves. Transmitter color sensi- 
tivities for primaries A are shown with 
solid lines. It should be understood 
that these sensitivities combine the color 
response of the light source, camera- 
tube photo-surface and color filters used 
at the camera. 

When examining the two groups of 
transmitter color characteristics in Fig. 
7, one will note that when disregarding 
the negative and minor positive lobes, 
the remaining shapes are almost identical 
except as to amplitude. Referring now 
to Fig. 5, the three transmitter charac- 
teristics for blue, green and red represent 



340 



October 1951 Journal of the SMPTE Vol. 57 



0.9 



O.I 0.2 0.3 0.4 0.5 0.6 0.7 




Fig. 2. Color triangle for receiver primaries E. 



Fig. 3. Theoretical (ideal) 
spectral sensitivities of the 
transmitter based upon re- 
ceiver primaries E. Note- 
White to be reproduced by 
equal voltages of the three 
primaries. 




400 450 50O 550 600 650 70O 

WAVELENGTH (MILLIMICRONS) 



Goldmark, Christensen and Reeves: Color Television 



341 




0.6 



0.7 



Fig. 4. Compara- 
tive fidelity of re- 
production of colors 
by means of trans- 
mitter primaries of 
Fig. 3 (using only 
positive lobes) to- 
gether with receiver 
primaries C and A, 
and type B Koda- 
chrome. Note Prim- 
aries A similar to 
primaries E. 



Legend : 

S = Published filter values 

O = Reproduced with primaries C 

JV = Reproduced with primaries A 

Numbers in brackets indicate approximate discernible 

color differences 
Numbers 13, 22, 32, 38 
Filters at 3,200 K 
P Reproduced with Kodachrome type B and 3,200 K 




450 500 550 600 

WAVELENGTH (MILLIMICRONS) 



Fig. 5. Standard transmitter 
color primaries, neglecting minor 
lobes and adjusted to produce 
equal signal amplitudes for red, 
blue and green (based upon 
receiver primaries E). 



342 



October 1951 Journal of the SMPTE Vol.57 



Legend : 

A Low flicker syn- 
thetic primaries, 
White = Illumi- 
nant C 

C Color Committee 
Primaries : #47, 
58, 25 Kodak 
filters + Illumi- 
nant C 
White = Illumi- 

nant C 

D (dotted line) 
CBS 2-phosphor 
with #47, 58, 26 
Kodak filters 
Triangle A = T b : 

r r :T g = 1:1.5: 

2.4 
Triangle C = T b : 

r r :T = 1:4.3: 

12.3 
Triangle D = T b : 

r r :T g = 1:4.9: 

13.4. 




0.7 



Fig. 6. Comparative color gamuts of receiver primaries A, C and D. 



Legend : 

I. Solid line = ideal trans- 
mitter color sensitivities for 
use with primaries A, re- 
producing white (Illumi- 
nant C) 

II. Broken line = ideal trans- 
mitter color sensitivities for 
use with primaries C, re- 
producing white (Illumi- 
nant C) 

Note White to be reproduced 
by equal-signal voltages of 
the three primaries. 




-i.o 



650 



400 450 500 550 600 

WAVELENGTH (MILLIMICRONS) 

Fig. 7. Theoretical (ideal) spectral sensitivities of the transmitter based 
upon receiver primaries A and C. 



700 



Goldmark, Christensen and Reeves: Color Television 



343 




400 *50 900 950 600 650 700 

WAVELENGTH (MILLIMICRONS) 

Fig. 8. Spectral transmittance 
curves of primary E filters. 

not only the major positive lobes of 
primaries E from Fig. 3 but also those 
of primaries A and C, and thus Z>, from 
Fig. 7. The electrical amplitudes re- 
quired to obtain the proper value of 
white at a receiver using receiver 
primaries E, corresponding to equal 
areas under the red, blue and green 
transmitter color sensitivities, are already 
taken into account in Fig. 5. 

From the foregoing it can be seen 
that a transmitter which radiates signals 
corresponding to Fig. 5 will satisfy the 
receiver primaries A, B, C and E. 
Naturally, for primaries other than E 
the relative intensities of the various 
primaries at the receiver have to be so 
proportioned as to obtain the desired 
value for white. 

Primaries E as shown in Fig. 2 are 
the product of the phosphor charac- 
teristic and specific filters. Such filters 
have been manufactured by Monsanto 
Chemical Co. and Eastman Kodak Co. 
in large acetate sheets. Figure 8 shows 
the typical transmittance curves. 



The universal transmittance curves as 
shown in Fig. 5 require certain tolerances 
if they are to be used as standard. The 
following is an attempt to interpret the 
color standards in such a fashion that 
the transmitter characteristics are specifi- 
cally defined, while at the same time 
permitting the utmost flexibility for the 
color-television receiver designer. 

Given a light source illuminating the 
scene to be televised and having a 
spectral energy distribution E, where E 
is the radiant flux per unit wavelength 
throughout the visible spectrum (400 
to 700 m/i (millimicron)), the overall 
spectral response comprises: 

(a) Spectral sensitivity S of the camera 
tube, defined as its response to unit 
radiant flux of spectrally homogeneous 
energy as a function of wavelength, 

(b) Spectral transmittances, R, B, 
G, of the red, blue and green color 
filters; spectral transmittances being the 
ratio of transmitted to incident radiant 
flux of spectrally homogeneous energy 
as a function of wavelength, 

(c) Color amplitude factors r, b, g, 
of the color mixer, defined as the re- 
spective ratios of the outgoing and in- 
coming individual color signals. 

The camera sensitivity, the color 
filters and the color amplitude factors 
shall satisfy the following four conditions: 



1. 



2. 



3. 



ESRdX / /-700 



/" 

/t 



500 
'410 



ESBdX 



too 



oo 



ESGdK 



/70( 
7400 



ESRd\ be not less 
than 0.90, 

'ESBd\ be not less 
than 0.90, 

ESGd\ be not less 



than 0.90, 

4. The color amplitude factors r, b, 
g, shall be adjusted so that the color signals, 
corresponding to a white test area* illu- 
minated by the light source E, are equal 
within 5%. 

* The white area of the test chart shall 
have a spectral reflectance substantially 
constant, independent of wavelength. 



344 



October 1951 Journal of the SMPTE VoL 57 



II. Commercial Color-Television Receivers 



IT is COMMON KNOWLEDGE that methods 
used by any color-television system for 
presentation of a color picture at the 
receiver may be used with the field- 
sequential system, while the converse is 
not true. Several of these methods are 
illustrated in Fig. 9. The majority are 
unsatisfactory for home use because of 
one or more of the following undesirable 
features: (1) difficulty of maintaining 
optical registration, (2) difficulty of 
maintaining electrical registration, (3) 
narrow viewing angle, (4) high cost, and 
(5) insufficient highlight brightness. 
Table II shows the undesirable features 
associated with each method. 

Table II 

Method Undesirable Features 

(From Fig. 9) 1 2 3 4 5 



a 


X 


X X 


X 




b 


X 


X 


X 


X 


c 


X 


X 


X 


X 


d 


X 


X 




X 


e 








X 


f 








X 


S 










i 




? 


? 





The direct-view color tube will likely 
offer a convenient method, when de- 
veloped to a commercial product at a 
reasonable price. Of the remaining 
tabulated methods, at present only the 
last three yield sharp color pictures 
usable in the home, and only the last 
two are capable of generating bright 
and sharp enough pictures for suitable 
home viewing in a normally lighted 
room. Both of these employ direct 
view with standard tubes; one uses the 
color disk and the other, the color drum. 

With proper arrangement of disk and 
raster, a color disk need be only slightly 
larger than twice the tube diameter. 
For home use disks larger than 27 in. 
(12^-in. tube, enlarged to 16-in. picture) 
have not been employed. The arrange- 



ment most frequently used is a 22^-in. 
disk in combination with a 10-in. tube, 
yielding a 12^-in. picture. 

The color drum provides large un- 
magnified color pictures within a reason- 
ably sized cabinet. Several types of 
drum color receivers built around 17-in. 
rectangular tubes have demonstrated 
excellent picture qualities. There is no 
reason why 20-in. or larger direct-view 
color pictures cannot easily be obtained. 

The color drum, first employed by 
CBS in 1940-41, will be described at a 
later date. The remainder of this paper 
will deal in some detail with two of the 
most recently developed commercial- 
type receivers employing the color disk. 
These are the combination color re- 
ceiver and the slave color receiver. 

Combination Color Receiver 

With the advent of standard com- 
mercial color television, a modern 
home television receiver should be 
capable of receiving equally well both 
monochrome and color. It should also 
have the ease of operation presently 
associated with monochrome receivers. 
The combination receiver here described 
satisfies .these requirements and is de- 
signed to sell at a moderate price. 

Physical Characteristics. The dual color 
disk drive used in the combination re- 
ceiver is shown in Fig. 10. The main 
chassis is shown in Figs. 11 and 12 and 
a detailed schematic is given in Fig. 13. 
Including rectifiers, 23 tubes are used. 
Except for the dual frequency scanning 
and the disk drive mechanism, the re- 
ceiver is essentially the same as a standard 
monochrome receiver; discussion will 
therefore be confined largely to these 
differences. 

A 10FP4 picture tube is used for both 
monochrome and color. In both cases 
a 12^-in. picture is obtained by means 
of an oil-filled lens fastened integrally 
with the front of the cabinet. In the 



Goldmark, Christensen and Reeves: Color Television 



345 




IS 

, ?I 









t 







>z 

Om 




fe 



I 

I 



346 



October 1951 Journal of the SMPTE Vol.57 





dual disk arrangement only one-half of 
each disk is covered with filters, the other 
one-half being transparent. This permits 
the disks to be relatively phased so as to 
provide between the tube and the 
observer continuous filters for color 
operation or, when stopped, only clear 
sections for monochrome operation. 
The disk assembly rotates between the 
tube face and the back of the lens. 

In this set, for the sake of economy, 
the color-pulse separator is omitted and 
the color disk is synchronized from the 
vertical pulses. Since these pulses con- 
tain no color information, a color-phasing 
button on the front panel is provided 
(which has to be pressed no more than 
twice) to obtain the correct colors. In 
other units, containing the color-pulse 
separator, this color-phase button, of 
course, is not required. 

A front panel color-monochrome 
switch permits manual selection of 
either of the two standards. When this 
switch is thrown to monochrome, the 
following takes place automatically: 
the scanning is changed to the mono- 
chrome rates; the dual disk is stopped 
with the clear disk sections superimposed; 
and the clear sections are rotated to a 
position over the tube face where no 
filters are visible. 



A 




93 



Color-Disk Drive Mechanism. An im- 
portant requirement for a color-disk drive 
mechanism and associated circuits is to 
maintain accurate disk phasing even 
when operating under changing tempera- 
tures, adverse conditions of varying line 
voltages and frequencies, and variable 
signal inputs. Further requirements are 
rapid acceleration of the disk to syn- 
chronism upon the application of power 
and short disk pull-in time, i.e., the time 
required to synchronize a disk after 
selecting a particular station. Moreover, 
electrical interference should be absent 
and weight, size, cost and mechanical 
noise should be a minimum. 

The combination receiver disk drive 
mechanism shown in Fig. 10 satisfies 



Goldmark, Christensen and Reeves: Color Television 



347 



these requirements. -Proper phase within 
2 over the normal range of operating 
temperatures is maintained with line 
voltages between 105 and 125 v and with 
line frequencies between 59.5 and 60.5 
cycles/sec. The unit generates no elec- 
trical interference, has no rubbing 
contacts, and operates with a minimum 
of mechanical noise and vibration. It 
is designed to operate with a standard 
motor, a toothed rubber-fabric belt 
drive, and other components relatively 
easy to obtain. 

As shown in Fig. 10 the dual disk as- 
sembly, generator, brake, and resiliently 
mounted induction motor are all fas- 
tened to a supporting baffle. Also 
mounted on the back of the baffle is 
the kinescope supporting structure. The 
disk housing is fastened to the front of the 
baffle by twist-lock screws. This hous- 
ing completely encloses the disk in a 



fairly airtight space. Such an enclosure 
is important in order to keep disk driving 
power to a minimum and to retard the 
accumulation of dust on the disk and 
picture tube face. 

The motor is a standard four pole 
capacitor induction type with the follow- 
ing operating characteristics: It delivers 
23 in.-oz. torque at 1748 rpm with 
80 to 85 v rrns input at 60 cycle/sec. 
It is also capable of delivering the above 
torque at 1764 rpm with approximately 
90 to 95 v input at 60 cycle/sec. This 
latter condition corresponds to operation 
at 1748 rpm at 59.5 cycle/sec. A 
centrifugal switch is provided internally 
which opens at approximately 1700 
rpm and closes at approximately 1600- 
1650 rpm; its purpose will be described 
later. 

The motor drives the disk shaft by 
means of a rubberized-fabric toothed 




348 



Fig. 10. Dual color-disk drive (cont'd. on next page). 
October 1951 Journal of the SMPTE Vol. 57 



timing belt, which maintains a constant 
speed ratio of 17/14 between the motor 
and the disk. With the disk rotating at 
1440 rpm the motor rotates at 17484- 
rpm. 

The front color disk is fastened solidly 
to the disk drive shaft, while the back 
disk floats on the shaft and is free to 
rotate back and forth with respect to 
the front disk through approximately 
^ revolution. A centrifugally operated 
catch mounted on the back disk, as 
shown in section A-A Fig. 10, prevents 
it from rotating backward beyond a 
predetermined point. At this point 
the catch actuates a microswitch whose 
function will be described later. 

When the disks are rotating rapidly 
forward the centrifugal catch with- 
draws and is inoperative, and the air 
drag on the back disk causes it to lag 
the maximum amount. Under this 




condition the filters on one disk are 
adjacent to the clear area on the other 
disk, thereby providing in front of the 
picture tube a succession of six color 
filters, as required for color operation. 

When the receiver is switched to 
monochrome, the brake is engaged and 
the motor is reversed. The disk as- 
sembly is rapidly brought to a stop and 
is then slowly rotated in a backward 
direction by the motor. The centrifugal 
catch stops the back disk, while the front 
disk continues to rotate until the back 
disk leads the front disk by the maximum 
amount, at which time the centrifugal 
catch actuates the microswitch, turning 
off the motor. This leaves the two clear 
areas of the disks adjacent to each other 
and over the tube face, as is required 
for monochrome. 

The brake mechanism consists of a 
simple friction plate notched on its 
periphery and mounted under tension 
between two felt plates keyed to the 
disk drive shaft. During operation, a 
stationary latch engages the brake plate 
at its periphery. 

The reluctance-type generator con- 
sists of a magnetically hard U-shaped 
stator with a coil around each leg and 
a magnetically soft rotor. It is mag- 
netized by discharging a heavy electro- 
lytic condenser through the coils while 
the generator is running. 

The stator and rotor pole pieces are 
shaped to provide a saw-tooth wave 
output of approximately 200 v peak-to- 
peak. This saw tooth has a very steep 
downward slope of approximately 10 
v per degree disk rotation, which limits 
the variation of disk phase to approxi- 
mately 2 over the wide range of 
operating conditions described pre- 
viously. 

Precision ball bearings with sealed-in 
lifetime lubrication are used to float 
the color disk drive shaft. These require 
no care, retain low and constant friction 
over a wide range of operating condi- 
tions, and eliminate any oil seepage onto 
the color disks. 



Goldmark, ChrUtensen and Reeves: Color Television 



349 




350 



October 1951 Journal of the SMPTE Vol. 57 








Ml 

u< 



Goldmark, Christensen and Reeves: Color Television 



351 



Chassis Component Placement. In the 
combination color-monochrome receiver 
it is necessary to switch components of 
normally isolated circuits, such as 
vertical deflection, horizontal oscillator, 
horizontal output, etc. This results in a 
somewhat different placement of chassis 
components than that normally used 
on monochrome receivers. As evident 
in Fig. 12, most color-monochrome 
switch contacts are connected to the 
so-called screw-driver controls located 
on the rear chassis skirt. A practical 
location of the switch is, therefore, 
adjacent to, and parallel with these 
controls. To maintain short leads, the 
components of the various horizontal 
and vertical deflection circuits obviously 
should also be located near their re- 
spective switches. 

The chassis layout of the combination 
receiver is shown in Figs. 11 and 12. 
Arranged in line along the rear of the 
chassis, are the vertical scanning circuits, 
the horizontal oscillator circuits and, 
under a perforated metal shield, the 
horizontal output circuits. Beneath the 
chassis, parallel to the rear "screw- 
driver" controls and under the corre- 
sponding circuits, is the ganged wafer 
switch. The switch is actuated by a 
connecting rod and rocking arm me- 
chanically linked to a knob on the front 
panel. 

The close placement of adjacent 
electrical components is evident from 
a cross-comparison of the schematic 
with the chassis arrangement. From the 
RF tuner, the signal travels a short path 
through the IF strip to the second de- 
tector and first and second video 
amplifiers. At the second video am- 
plifier the signal branches to the audio 
and the synchronizing separator cir- 
cuits; from there it travels over short 
paths to the vertical and horizontal 
scanning sections. 

The power supply and color disk 
synchronizing circuits are mounted on a 
separate small chassis. Components 
sensitive to a 60-cycle/sec magnetic 



field, such as the picture tube and 
vertical oscillator, are thereby separated 
from the power transformer, the filter 
choke and the saturable reactor. 

It is very important that the 60-cycle/ 
sec component be kept to 50 db below 
the peak-to-peak color signal in both 
video and synchronizing circuits. Larger 
amounts may be characterized by 
horizontal jitter, vertical jitter, picture 
flutter, poor interlace, etc. The 60- 
cycle/sec component may be injected 
by the magnetic fields mentioned above, 
by filaments, or by power supply ripple. 
One of the most sensitive areas with 
respect to magnetic fields is the neck of 
the picture tube. In earlier receivers 
this tube was shielded with a mu-metal 
funnel. In the combination set, how- 
ever, the overall hum is reduced to the 
desired low level by properly orienting 
components radiating 60 cycle/sec, 
by using a well-filtered power supply, 
and by observing the usual practices of 
twisting filament leads, etc. 

RF, IF and Video Circuits. Since the 
horizontal scanning rate of color pictures 
is approximately twice that of mono- 
chrome, it is important to preserve the 
higher video frequencies. In addition, 
it is necessary that the video output be 
as linear as possible over the entire 
video band in order to avoid contrast 
distortion in the color picture. Such 
distortion is less noticeable in mono- 
chrome, since in color television it 
manifests itself as poor color rendition. 

It has also been found desirable to 
switch both contrast and brightness 
when switching from monochrome to 
color, since an optimum color picture 
as seen through the color disk has 
excessive brightness and contrast when 
seen in black-and-white without disk. 

The RF-IF section is composed of a 
standard Sarkes-Tarzian tuner, two 
tuned IF pairs in cascade, and a second 
detector. Its response is essentially flat 
to 3.7 me (megacycles) and is down 3 
db at 4 me. 



352 



October 1951 Journal of the SMPTE Vol.57 



The video amplifier consists of one- 
half a 12AU7 triode first video stage 
and a 6AQ5 output video stage. The 
second half of the 12AU7 is used as a 
d-c restorer. With three volts peak-to- 
peak input, 120 v peak-to-peak are 
realized at the kinescope grid. The 
6AQ5 stage is capable of 1 30 v peak-to- 
peak without appreciable amplitude 
distortion. 

A degenerative-type contrast control 
in the 6AQ5 cathode circuit is frequency 
compensated to provide essentially uni- 
form frequency response throughout the 
control range. For monochrome the 
maximum video level is lowered by 
switching a 560-ohm resistor into the 
contrast control circuit. 

Audio Circuits. These circuits are 
identical to those used in monochrome. 
The IF trap attenuates the sound carrier 
approximately 10 db. The 4.5-mc inter- 
carrier signal is removed from the plate 
circuit of the video output stage. A 
6AU6 amplifier drives a 6T8 stage, 
which is a combination ratio detector 
and first audio amplifier. Additional 
audio amplification is provided by the 
6V6GT audio output stage, which also 
acts as a dropping resistor and regulator 
for the 150-v supply. 

Synchronizing Circuits. Synchronizing 
signals are derived from the 12VH7 
first video amplifier. This provides 
signals of essentially constant amplitude 
independent of contrast adjustment. 

The noise immunity of the synchroniz- 
ing signal separator is improved through 
the use of a combination long- and short- 
time-constant coupling circuit. The 
usual phase-inverter type second triode 
delivers the separated signals to the 
vertical oscillator and the horizontal 
phase detector diode. 

Vertical Oscillator and Output Amplifier. 
A 12BH7 is used as a vertical blocking 
oscillator and output stage. Necessary 
circuit changes between color and 



monochrome are provided by five 
SPDT switches which act at the follow- 
ing points: (1) vertical oscillator grid 
return resistor (vertical hold), (2) RC 
charging network in the plate circuit 
of the vertical oscillator, (3) height 
controls, (4) linearity controls, and 

(5) centering controls. 

Horizontal Oscillator and Output Ampli- 
fier. A 6AL5 phase detector controls the 
12BH7 horizontal multivibrator in the 
usual manner. A 6BG6G horizontal 
output tube, a 6U4GT damper and a 
pair of 1X2 voltage doubling rectifiers 
provide adequate 55 scan and a h-v 
potential of approximately 1 5 kv. 

Nine monochrome-color SPDT 
switches provide circuit changes at the 
following points: (1) AFC time-constant 
capacitor in the grid circuit of the hori- 
zontal oscillator, (2) flywheel LC tuning 
capacitor in the plate circuit of the 
horizontal oscillator, (3) fixed resistor 
in series with the horizontal hold control, 
(4) horizontal drive control potentiom- 
eters, (5) RC charging network in the 
output of the horizontal oscillator, 

(6) 6BG6G screen voltage, (7) yoke tap 
on the horizontal output transformer, 
(8) width controls, and (9) centering 
controls. 

A special horizontal output trans- 
former developed specifically for use on 
both color and monochrome frequencies 
is employed. The construction of this 
transformer is conventional and a ferrite 
core is used. Pertinent constructional 
details are shown in Fig. 14. 

In this type of dual-frequency trans- 
former the leakage reactance may 
resonate with the distributed capaci- 
tance, resulting in undesirable "ripples" 
on the left edge of the raster. This 
effect is eliminated in the combination 
receiver by connecting, for monochrome, 
a highly damped tuned circuit in the 
transformer secondary. As indicated 
in Fig. 13, this circuit is a parallel 
combination of a 200-juh (microhenry) 
inductance, a 1000-/i^f (micromicro- 



Goldmark, Chris tense n and Reeves: Color Television 



353 



OLYETHYLENE 
WIRES 6" LONG 




TWO TURNS EACH ON BAKELITE 
10" POLYETHYLENE LEADS 



2T 



1 


2 


900 


i 



o 


3 
4 


501 


500.^ 







5 


300 


I 

35 


E 6 o 



CAM 0.156 

GEAR 72-29 

WIRE 38SSEORSNE 

CAM 0.5 

GEAR 30-67 

WIRE 34 SSE ORSNE 

CAM 0.75 

GEAR 30-88 

WIRE 28 SSE OR SNE 



Fig. 14. Dual frequency horizontal output transformer. 



farad) capacitance, and a 5000-ohm 
resistor. 

A conventional monochrome anastig- 
matic scanning yoke is used. This again 
employs a ferrite core. The vertical 
and horizontal windings are of a type 
with inductances of 50 mh (millihenry) 
and 8.3 mh, respectively. 

Color Disk Synchronizing Circuits. As 
indicated in Fig. 13, a pulse gate, a 
phase detector, and a saturable reactor 
control tube are used for color disk 
synchronization. The saw-tooth wave 
produced in the disk shaft generator is 
applied to both sections of the phase 



detector tube. This tube conducts mo- 
mentarily only when excited by the 
vertical pulses. The clamped voltage 
appearing at the grid of the control tube 
is therefore dependent upon the relative 
phase relationship between the vertical 
pulses and the locally generated saw- 
tooth wave. A variation of control tube 
current causes a corresponding change 
in the degree of saturation of the motor 
control reactor, thereby varying the 
speed of the color disk. 

If, for example, the disk momentarily 
slows to slightly below synchronous 
speed, the point on the locally generated 
saw-tooth wave at which the vertical 



354 



October 1951 Journal of the SMPTE Vol. 57 



pulses clamp moves upward, thereby 
decreasing the bias on the control tube. 
The increased control tube current 
increases the degree of saturation in the 
motor control reactor, thereby increasing 
motor and disk speed to synchronism. 

The pulse gate provides velocity 
correction of the color disk. This tube 
is normally conducting, thereby pre- 
venting the vertical pulses from reaching 
the phase detector. The locally gener- 
ated saw-tooth wave from the generator 
is differentiated and applied to the grid 
of the gate tube in such a manner as 
to make it nonconducting only during 
the downward steep portion of the saw- 
tooth wave. Thus the operation of the 
phase detector is permitted during this 
period only. With this arrangement 
the average bias appearing at the control- 
tube grid is high when the disk is running 
considerably over speed, and low when 
running considerably under speed. This 
provides effective disk velocity correction. 

In the color disk synchronizing cir- 
cuits, as in most servomechanisms, an 
anti-hunt network is required to elimi- 
nate hunting. Such a network is pro- 
vided by the 20,000-ohm resistor, 16- 
/uf electrolytic capacitor, and 2-/*f paper 
capacitor at the screen of the control 
tube and the 250,000-ohm potentiometer 
between the saw-tooth generator and 
ground. This network returns from the 
control tube to the phase detector the 
necessary amount of phase-shifted antic- 
ipating voltage to prevent hunting. 
Optimum anti-hunt adjustment is pro- 
vided by the 250,000-ohm potentiometer. 

Changes in type of color disk (as to 
its inertia), motor, or saturable reactor 
usually require corresponding changes 
in the anti-hunt feedback network. 

Color Disk Synchronizing Operation. In 
effect, three separate operations pull the 
disk into synchronism and keep it there. 
When power is first applied, the centrif- 
ugal switch in the motor is closed, 
shorting the a-c windings of the saturable 
reactor. Full line voltage is thereby 



applied to the motor, causing rapid 
acceleration of the color disk to near 
synchronous speed. The centrifugal 
switch then opens and the saturable 
reactor with its associated circuits takes 
control. The velocity correcting circuits 
bring the disk to synchronous velocity, 
at which time the phasing circuits bring 
the disk into exact phase and maintain 
it there. Only ten to fifteen seconds is 
required to bring the 22j-in. disk into 
synchronism and phase from a standstill. 
When running, the disk synchronizes in 
less than one second. 

Power Supply. The power supply in 
the combination color-monochrome re- 
ceiver is similar to that of any good 
monochrome receiver. As discussed 
previously, both the 60- and 120-cycle/ 
sec hum components are kept very small. 
Decoupling is provided between the 
terminals supplying the disk synchroniz- 
ing circuits and those supplying the 
remainder of the receiver. This elimi- 
nates any low-frequency variation of 
picture size, brightness, etc., induced 
by the action of the color disk syn- 
chronizing circuits. These circuits re- 
quire a relatively constant current of 10 
to 30 ma (milliampere) while the disk is 
in synchronism, but during the time the 
disk is being pulled into synchronism the 
current may vary at a slow rate between 
approximately and 60 ma, with a 
corresponding induced variation in 
power supply voltages. 

Two 5V4G cathode-type rectifiers 
prevent high-voltage surges when the 
receiver is first energized. After filtering, 
390 v at 240 ma is available. 

A selenium half-wave rectifier is 
connected to one side of the high- 
voltage winding of the power transformer 
to provide the negative voltages for the 
electrostatic picture tube focus and the 
disk control circuits. 

Slave Color Receiver 

Of universal interest to present tele- 
vision set owners is how to use present 



Gold mark, Christen sen and Reeves: Color Television 



355 






JMD 

- 



356 



October 1951 Journal of the SMPTE Vol. 57 




1 



3 

V) 



00 



II 




Goldmark, Christensen and Reeves: Color Television 



357 




358 



October 1951 Journal of the SMPTE VoL 57 



monochrome sets to receive color. 
While adaptors may be used to permit 
reception of color broadcasts in black- 
and-white, and converters may be used 
to change these to color, a preferred 
method is that of using a slave color 
receiver. This unit scans at color fre- 
quencies only and presents a color picture 
by means of its own separate tube and 
color disk. It requires from the mono- 
chrome receiver only composite video. 
Sound is derived from the monochrome 
receiver in the usual manner. Since 
the slave receiver requires no RF, IF 
or audio stages, it is considerably less 
expensive than a complete color receiver. 
The slave color receiver is shown in 
Figs. 15 and 16; the chassis is shown in 
Figs. 17 and 18; and its schematic is 
given in Fig. 19. Requirements for the 
various sections of this receiver are 
essentially the same as those described 
for the combination receiver. A few 
departures, however, are described in 
the following paragraphs. 



Physical Characteristics. The overall di- 
mensions of the slave color receiver are 
somewhat less than those of the combina- 
tion receiver, being 27J in. wide by 
33 in. high by 20 in. deep. Sixteen 
tubes are employed, including rectifiers. 

Only a single chassis is used, the power 
supply and color disk drive components 



being arranged in such a manner as to 
produce no undesirable effects from 
their magnetic fields. 

The lower of the two front panel knobs 
controls the off-on switch and the con- 
trast. The upper knob is rotated to 
control the brightness and depressed 
to bring the color disk to the proper 
phase. 

Video Circuits. Two stages of conven- 
tional design are employed. Video 
response is flat within 2 db from 30 
cycle/sec to 4 me with a voltage gain 
of approximately 115. A 4.5-mc sound 
trap in the 6AQ5 screen circuit provides 
35-db rejection. A polarity reversal 
stage with unity gain provides operation 
with either polarity of incoming com- 
posite video. Since the contrast control 
is mounted at a distance from the chassis, 
a somewhat unconventional circuit is 
used in which a variable positive bias 
is applied to the cathode of the first 
video stage. With the constants used 3 
this circuit gives adequate contrast range 
with negligible frequency discrimination. 

Vertical Oscillator and Amplifier Circuits. 
To insure reliable interlace these circuits 
are placed in a shielded compartment. 
This eliminates interference from both 
nearby electrical fields and from the 
magnetic fields of the power transformer 
and saturable reactor. 



III. CBS Color-Television Broadcast Facilities 



Conversion of the RCA Monochrome 
Field Camera for Color Television 

The first prototype conversion of the 
RCA Field Television Camera Chain 
was undertaken by the RCA Terminal 
Facilities Engineering Group in Camden, 
N. J., between May and July of 1950. 
Circuit changes and additions, which 
CBS had used satisfactorily in earlier 
color television equipment, were in- 
corporated into several sections of the 
converted equipment. During 1950 a 



second and third camera chain were 
converted in the CBS General Engineer- 
ing Department, incorporating improve- 
ments resulting from experience gained 
through use of the first equipment. 
These, and a few additional improve- 
ments, are now being incorporated in a 
new series of color camera chains, again 
using standard monochrome equipment 
as a basis. 

In the first three conversions type TK- 
30A field camera chains with studio 



Goldmark, Christensen and Reeves: Color Television 



359 




Fig. 20. RCA monochrome camera converted for 
color, front view; lens turret removed and added 
color disk in place. 





~ 


VIEW 
FINDER 




* 


STUDIO 
CAMERA 


] 






FIELD 
POWER 
SUPPLY 


FIELD 
CAMERA 
CONTROL 


*COLOR 
MIXER 
UNIT 




FIELD 
PULSE 
SHAPER 








t 


J 


*COLOR 
MONITOR 


FIELD 
POWER 
SUPPLY 


FIELD 
PULSE 
FORMER 






ONE CAMERA 'CHAIN* 






r~ 

COMPOSITE 
SIGNAL 
TO LINE 










FIELD 
SWITCH 
SYSTEM 


FIELD 
POWER 
SUPPLY 




INTE 


1 




ROOM 


X 


MASTER 
COLOR 
MONITOR 



Fig. 21. RCA mono- 
chrome camera converted 
for color; top view, show- 
ing color drive assembly 
with added color-disk 
drive motor. 



* These units in o single assembly 



Fig. 22. RCA single camera chain con- 
verted for color, block diagram. 



type RCA Ml 26000 cameras were used. 
Figures 20 and 21 show how the color 
disk housing on these cameras is in- 
corporated in a new front cover. Since 
the studio and field type cameras are 
identical as to circuit and chassis con- 
struction, the field camera with similar 
mechanical changes to the cover can 
also be successfully modified. 

A block diagram showing the signal 
connections of a single camera chain, 
complete with synchronizing signal gen- 
erator, is shown in Fig. 22. It will be 
noted that the connections are identical 
to those used for monochrome except 
for the addition of cables to the color 
mixer amplifier. The modifications 
necessary to each of the units shown in 
Fig. 22 will be described in some detail 
in the following sections. 

Synchronizing Signal Generator Pulse 
Former. The principle changes to this 
unit are: 



360 



October 1951 Journal of the SMPTE Vol. 57 



(a) Shift the master oscillator hori- 
zontal scanning frequency to 58,320 
cycle/sec. 

(b) Change the cathode bias re- 
sistors of the counters so that the first 
three counters count down 9-9-5 to 
give the 1 44-cycle/sec vertical trigger- 
ing pulse, and the fourth counter counts 
down, 3 to 1 , to give the color triggering 
pulse. 

(c) Install three double triode 
miniature tubes on a small shelf mounted 
between terminal boards. These gen- 
erate a color drive pulse and a color 
synchronizing pulse; both at a 48-cycle/ 
sec rate. The color drive pulse is used 
for two purposes: first, to provide a 
trigger pulse for the color mixer red- 
gating circuit so that the red video 
channel is always properly identified 
(to be further described later); second, 
to provide a variable time delay to 
center exactly the timing of the color 
synchronizing pulse between the first 
and second equalizing pulses. 

The color synchronizing pulse is 
introduced over an unused terminal 
and cable connection into the pulse 
shaper unit, where it is mixed with 
composite synchronizing signal. 

The above describes an earlier method 
of generating a color synchronizing 
pulse, and while convenient it is not 
satisfactory when using step counters, 
since there is excessive time delay 
between the front edge of the original 
58,320-cycle/sec trigger pulse and that 
of the 48-cycle/sec pulse from the fourth 
counter. 

A more recent method is indicated in 
Fig. 23. A sufficiently wide color drive 
pulse, b, is generated to gate in only the 
first equalizing pulse of every third field. 
This single equalizing pulse, which does 
not shift in time phase, is used to trigger 
the color delay multivibrator. The 
resulting pulse is in turn differentiated 
and its trailing edge is used to trigger 
the color synchronizing pulse multi- 
vibrator. The width of the delay pulse 
thus controls the start of the color pulse 



generator, and the width of the color 
synchronizing pulse can then be adjusted 
to the required value of 0.04 H. The 
color synchronizing pulse should be 
properly centered between the first 
and second equalizing pulses by use 
of a trigger-time-base oscilloscope. 

It is preferable to supply power for 
the filaments and the master oscillator 
lock-in from a small 1 44-cycle/sec 
generator driven by a synchronous mo- 
tor. This avoids 60-cycle/sec phase 
modulation in the generated pulses due 
to poor filament grounds or common 
cathode-filament ground returns. Three 
miniature tubes on a small sub-chassis 
are used to generate a 60-cycle/sec 
comparison pulse for afc locking. This 
unit counts down 12 to 1 from the 720- 
pulse/sec output of the second counter. 
In some conversions a 4-to-l and a 
3-to-l counter were used to obtain the 
12-to-l ratio with better stability. No 
problems were encountered in operating 
synchronizing signal generators expressly 
designed for color standards on a 60- 
cycle/sec power source. 

Synchronizing Signal Pulse Shaper. In 
order to produce the pulse width re- 
quired for the higher scanning speeds, 
RC changes are necessary in all the 
multivibrator pulse generating circuits. 
Pulse slopes with fast enough time-of- 
rise to meet FCC standards as shown in 
Fig. 1 can be obtained without diffi- 
culty. To inject the color synchronizing 
pulse directly into the synchronizing 
pulse mixing and clipping circuits, a 
small miniature tube is mounted on the 
chassis with its plate circuit connected 
in parallel with the composite syn- 
chronizing pulse mixing tubes. 

Camera. Two major changes are 
required in the camera: (a) a new 
horizontal scanning circuit to supply the 
higher scanning power necessary for 
camera tube deflection; and (b) the 
addition of the color disk to the front 
end of the camera with accompanying 



Goldmark, Christensen and Reeves: Color Television 



361 



><'*> 




362 



October 1951 Journal of the SMPTE Vol. 57 



mechanical modifications of the focusing 
mechanism. 

The horizontal scanning circuit used 
in the second and third conversions has 
proved entirely reliable in extensive use 
in industrial color camera equipment. 
This circuit is shown in Fig. 24. The 
normal output transformer is replaced 
with a specially designed transformer 
using grooved textolite and formex 
forms placed over dual three-mil lami- 
nated hypersil cores. 

Instead of the +360-V unregulated 
source normally used, the damping tube 
is used to provide a rectified boost 
voltage. This avoids any 120-cycle/sec 
ripple component that might cause a 
24-cycle/sec phase jitter in the horizontal 
scanning. As in black-and-white serv- 
ice, a scanning current of 1 amp peak- 
to-peak is normally required. This 
circuit, however, is capable of supplying 
a linear scanning current of 1.3 amp 
peak-to-peak, which allows sufficient 
overscanning to prevent burn-in of the 
mask on the target. 

Installation of the color disk drive 
assembly requires that the lens turret 
and light trap be moved forward and 
that the front face plate of the camera 
be replaced. To permit all lenses to 
be focused to infinity, the back edge of 
the camera tube bakelite mask retainer 
ring is undercut by approximately f in. 
This allows the tube to be pushed 



sufficiently forward into the focus coil 
assembly. 

The color disk, which rotates at 720 
rpm, is mounted directly on the end of 
a j-in. shaft which extends lengthwise 
through the top portion of the camera 
and runs in oilite sleeve bearings 
mounted on the new front face plate 
and the rear of the camera chassis. At 
one end of the shaft is mounted a 
twelve-tooth sprocket which is coupled 
to a six-tooth sprocket on the motor 
by means of a Gilmer timing belt (mold 
No. 9164). The motor is a one- 
hundredth horsepower salient pole syn- 
chronous type (Cyclohm model No. 
SWC2914-XL). It operates from a 
48-cycle/sec, 115-v, 25-w amplifier lo- 
cated in the color mixer chassis. This 
arrangement permits continuous elec- 
trical phase adjustment. Proper phase 
adjustment occurs when the spokes of 
the disk, separating adjacent color 
filters, coincide with the locus of the 
scanning beam in the camera tube. 
This condition is necessary in order to 
avoid color carry-over from one field 
to the next. Since the optical image is 
inverted on the photocathode and the 
raster is therefore scanned from bottom 
to top, it follows that the disk, as viewed 
in Fig. 20, must turn clockwise. To meet 
the colorimetric requirements discussed 
previously in this paper, No. 25 red, 
No. 47, half-density blue, and No. 58, 





- 












f = 


x 

11 




= 












=3 = 


-r 




- 












1 

i 


a o 

si! 


















a -si 
































i 


Tl 
















i 


.SP ^ a 


T 








....id 






i 


IJ 


4M*1 


m " mm \ 











t ^ ^ jg 




- t 5 




o- M a 



Goldmark, Christensen and Reeves: Color Television 



363 




three-quarters density green color filters 
are used.* 

Camera Viewfinder. The circuit modi- 
fications in the viewfinder are of a minor 
nature, mostly involving RC changes. 
The original deflection yoke and trans- 
former may be retained if the horizontal 
coils of the yoke are reconnected in 
parallel in order to obtain a sufficiently 
fast retrace. This is required since the 
narrow image-orthicon target blanking 
derived from the vertical and horizontal 
driving pulses is used for blanking of the 
picture tube in the viewfinder. 

Camera Control Unit. In this unit it is 
necessary to: 

(a) Substitute a 7RP4 picture tube for 
the 7CP4. This provides a brighter 
picture as is desirable for monitoring 
in color; 

(b) Add a high-voltage supply of at 
least 10,000 v (for the 7RP4 picture 
tube) ; 

(c) Modify the horizontal scanning 
circuit; 

(d) Provide mechanical modifications 
necessary to mount the new tube in 
place; and 

(e) Move the front panel controls to 
provide space for a color disk and its 
enclosure in front of the picture tube. 

Not all of these changes are necessary 
if the original 7CP4 picture tube is used 
as a monitor in black-and-white (color 
standards without color disk). In this 
case it is advisable to include a picture 
monitor in color in the color mixer. 

With this latter arrangement, i.e., 
black-and-white monitoring of the color 
picture, the camera control unit need 
be modified only as follows: 

(a) Connect the output of the fourth 



* Numbers refer to published transmit- 
tance characteristics for Wratten filters. 

Fig. 24. Horizontal scanning circuit 
for image orthicon tube used in RCA 
camera converted for color and in in- 
dustrial color television camera. 



364 



October 1951 Journal of the SMPTE Vol.57 



.?. is. 

a* vs* 

lo! zo! 

3 



pay 6uiXa>| anjg buiXax uaajg buiXax 

JO) pasn JO) pasn JO) pasp 

I I 



m 
a. 


















1 1 


r 










! 

i 


= 







-- 


ij 




r 




LI 


i 






] 


, 


L 

>o 

V > 

1,^ 
















1 














1 









i 






_ _ 












J 








* 
i 


o c 

r- 

?> 


1 

> 


1 < 


i_ 

> 000 

N- f 


o 1 


o 




~i 

o 




J 


<WNr 

+ 

^/W- 

$ 




n- 

HM 

15 

Q. 

A] J 

CH 


> v 
:<^ 

V 

: 


/v 

-T 

Hh- 

s/v 


S 

1- 


! 

! 

*w*- 

^/v- 


_T' W L 
-ij- 

T Q i^ 

0* 

oT 
> 1^ 

r^i 

^^ ,. i 


/V 

O 

>/v 


i 
i 




vw 

> 
vw 

Jl 


2 

-C3- 

of 

> 


> 

a 
i 

wv 

^ 

vw 


6 *- 

sl 






h 


S 

5 




,1 


U 












: - 



Goldmark, Christensen and Reeves: Color Television 



365 



1* 



>3 



4 J 

! 







y 


\SJ 




V ^ ) 


^ 


"vjy 


px,, 
I 




^ 




| 









1 




Q. 


^ 


! 




I 




I 




| 




m 




1 






> 
g 




, > 

>? 




>? 




^=r^= 


^-n 


2t-L~-.= 


: 


S.! ' 


V* 


i)a 


3 


r)k 


-Hi! 


<r)^ 



fc 




"'jfcJTrll 

II II fl I U B 8 fl I I I 

>> 





IDJUOZJJOH 



i Pi 4 
it h*iiii 

ilillrf 

II II II It U fl II 



IOJJUOQ DJiOIDO UJOJ 

indui 



9Sf*i!s< g>>>^ 



366 



October 1951 Journal of the SMPTE Vol.57 



video stage to an output jack by means 
of a 6AG7 tube with a low-impedance 
plate coupling circuit. The signal from 
this point may be passed through an 
external connection to a color mixer, 
for color mixing and injection of blank- 
ing. The signal is then returned to an 
input jack on the control unit, where 
the signal is further amplified in the 
normal manner. Since blanking is not 
used in this camera control unit, tube 
V8 can be removed and the additional 
6AG7 tube can be installed in its place. 

(b) Parallel the horizontal yoke coils 
and install a new horizontal output 
transformer of the type used in color 
receivers. These circuits should be 
powered from the regulated d-c supply. 
The boost winding should be used to 
provide the additional plate voltage 
required. 

(c) Provide a definite color sequence 
presentation on the waveform monitor 
so that both the amount of red, blue and 
green video signals and the blanking 
constants can be observed and indi- 
vidually adjusted. The 48-cycle/sec 
color drive pulse can be applied to the 
synchronizing circuit of the vertical 
sweep, preferably through tube V6, 
connected as a cathode follower. This 
provides the necessary isolation to pre- 
vent kickback into the color drive 
circuits. 

Color Mixer Unit. One color mixer 
unit is added to each camera chain. 
Its main purpose is to channel the video 
signal into three separately adjustable 
amplifiers, each amplifying only one 
color and each being turned on se- 
quentially, i.e., when the image is 
televised through the red filter, the video 
signal is amplified only in the red video 
channel. 

Figure 25 illustrates the color-gating 
pulse generator which controls the opera- 
tion of the color mixer. A functional 
block diagram of the color mixer is 
shown in Fig. 26. The color mixer 
front view and rear view is shown in 



Fig. 27. This unit with cover removed 
is shown in Fig. 28. In this unit 
composite receiver blanking is injected 
in the normal manner, clipped, ampli- 
fied and if so desired, returned to the 
camera control unit for further addition 
to synchronizing signals. 

For the accurate rendition of delicate 
color shades a gamma correction ampli- 
fier is incorporated to compensate for 
the compressed black output of the 
typical kinescope (light output vs. 
signal output). 

The 48-cycle/sec, 115-v power re- 
quired by the camera disk motor is 
derived as follows: The color drive 
pulse actuates a multivibrator to generate 
a 48-cycle square wave, which is con- 
verted to a sine wave by filtering out 
all harmonics above 48 cycles. The 
resultant signal is coupled through a 
selsyn motor to a push-pull output 
amplifier. A standard 5000-ohm output 
transformer is used to couple the 
amplifier to the camera disk motor. 
As mentioned previously, the selsyn 
permits convenient and accurate adjust- 
ment of the color disk phase with respect 
to camera scanning. The circuit ar- 
rangement for the camera disk motor 
power supply is also shown in Fig. 26. 

Regulated Power Supplies. Originally, 
additional filtering was required on the 
-4-360-v unregulated terminal since 
power from this terminal was used for 
horizontal camera scanning. In later 
conversions, however, only the hori- 
zontal scanning circuit of the view- 
finder is operated from this terminal and 
the horizontal camera scanning is con- 
nected to the regulated source. If a 
slight amount of 1 20-cycle/sec ripple 
in the 360-v terminal causes interference 
in the horizontal scan of the viewfinder, 
a small 4-h, 80-ma, choke in conjunction 
with a 10-microfarad, 600-v capacitor 
will prove helpful. 

General Considerations. No difficulty 
should be experienced in operating the 



Goldmark, Christensen and Reeves: Color Television 



367 





Fig. 27. Color mixer for RCA camera chain converted for color, 
front view and rear view. 




368 



Fig. 28. Interior of unit of Fig. 27. 
October 1951 Journal of the SMPTE Vol. 57 




Fig. 29. Studio 57 stage with two color cameras. 




Fig. 30. Sketch of Studio 57 control room showing the director, assistant director, 
technical supervisor, monitoring operators and monitoring equipment. 



Goldraark, Christensen and Reeves: Color Television 



369 




370 



October 1951 Journal of the SMPTE VoL 57 



Fig. 31. Color television signal dis- 
tribution system, block diagram. 



A.O.&An.Mn. - 

C. - 

C.C.N. - 

CL.MN. - 

CL.MX. - 

CLP. - 

COMP. - 

F.GL.MN. - 

I.A. - 

L.WF.O. - 

L. CL.MN. - 

RC. 

S.G. 

SL.SS. 

SW. & L.A. 

ST.A. 

T. 



audio operator, announcer 

and monitor 
camera 

camera control 
color monitor 
color mixer 
clamper 
composite 

floor color monitor 
isolation amplifier 
line waveform oscilloscope 
line color monitor 
receiver 
sync generator 
selector system 
switcher and line amplifier 
stabilizer amplifier 
transmitter 



entire camera chain from a 60-cycle/sec 
source if a synchronizing signal generator 
originally designed for color television 
is used and if common cathode-filament 
leads and all inadequate ground leads 
are eliminated. As an alternative, a 
synchronized 1 44-cycle/sec motor gener- 
ator can be used to power all filaments 
and the synchronizing generator shaping 
units. A 1500-w unit is adequate for 
a two-camera chain. 

The inter-lock circuits should be so 
connected that the regulated supplies 
of the two chains can be turned on only 
if the separate power input for the 
filament transformer is energized (with 
either a 60- or 1 44-cycle/sec, 115-v 
source). 

Identical procedures to those used in 
monochrome may be employed in 
operating and adjusting the camera 
control and tube voltages of the color 
chains. 

Film and Slide Scanning Equipment 

One method of color film scanning 
has been described in detail in this 
JOURNAL. 4 Another method makes use 
of an intermittent-type motion picture 
projector to project the color film 



4 Bernard Erdc, "Color television scanner," 
Jour. SMPE, vol. 51, pp. 351-372, Oct. 
1948. This scanner uses an image- 
dissector tube and continuously moving 
film. 



through a shutter directly onto the 
image-orthicon photocathode. 

The projector is a monochrome type 
used for 16-mm film at 24 frame /sec. 
The projector is driven by a synchronous 
motor and is thereby locked to the 
144_ C yde/sec field rate of the color 
system. Between the projector lens and 
the color camera a light shutter rotates 
which has a multiple of three slots. If 
the shutter rotates at 48 rev/sec, three 
slots are required, and the width of each 
slot is such that the duration of exposure 
is less than the vertical blanking time. 
This shutter is also driven by a phase - 
able synchronous motor. The proper 
red, blue and green color filters cover 
the shutter openings, and the projector 
and shutter disk are so phased with 
respect to the camera scanning that 
successive red, blue and green color 
images are flashed onto the camera 
tube photocathode only during vertical 
retrace times. The pulldown time of 
the projector is of short enough duration 
so that the film moves 24 times/sec only 
during portions of the active scanning 
period. In that period, however, the 
light from the projector is cut off by the 
opaque sections of the slotted disk. 

Two methods have been used to scan 
color slides. One, using an image- 
dissector tube, has been described, 4 
together with the film scanning method. 
In this arrangement the slide projector 
and its color disk replace the film 
scanner; the images are projected 
directly onto the photocathode of the 
dissector tube. 

The second method consists simply of 
projecting the color slides at low light 
intensity directly into a conventional 
image orthicon-equipped color tele- 
vision camera. 

Studio Lighting for Color Television 

In general, flat lighting over the entire 
stage area gives best results for color 
television. A certain amount of model- 
ing may be desirable, in which case 
ordinary spotlights are satisfactory. 



Goldmark, Christensen and Reeves: Color Television 



371 




Fig. 32. Industrial color television equipment; camera and control console. 




* 



Fig. 33. Industrial color television camera, front view. Tripod not shown. 




For overall flat key lighting 3500 K 
(white) fluorescent lighting is excellent. 
The advantages of this type of key 
lighting are that it contains no infrared, 
is relatively shadowless, generates little 
heat and is relatively efficient. The 
fluorescent lamps for key lighting can 
be operated from a standard three- 
phase 60-cycle/sec supply but must 
be ceninbeted in such a manner that 
all three phases are represented in any 
three aoljacent bulbs. 

Spotlights for modeling should be 



infrared corrected. This can be ac- 
complished by means of one-inch strips 
of Aklo No. 3962 glass (or equivalent) 
placed in front of the spotlight. The 
strips prevent the Aklo filter from 
cracking with absorption of radiated 
heat. 

If incandescent lighting with a color 
temperature of 2900 K is used, it is 
advisable to provide infrared filtering 
by using an Aklo No. 3962 (polished) 
glass filter between the camera lens and 
image-orthicon tube. Since each Aklo 



372 



October 1951 Journal of the SMPTE VoL 57 



filter attenuates the visual spectrum by 
approximately 50%, it is preferable, 
when possible, to employ the newly 
developed interference heat filters. One 
type already tested, known as type 
EK-227, passes the visual range with an 
efficiency of almost 90%, while the 
infrared energy is attentuated by 91%.* 

Standard photofloods furnish satis- 
factory lighting for color studio use, 
but naturally are short lived. In most 
cases infrared filtering is not required 
with this type of lighting. Lamps used 
in clusters and floor strips provide an 
excellent source of light. These have 
color temperatures of approximately 
3200 K and require only mild infrared 
correction. 

As to light level requirements, ex- 
perience has shown that 200 ft-c (foot- 
candles) infrared-corrected incident light 
will permit sufficient stopping down of 
the camera lenses to provide an adequate 
depth of focus. On the other hand, 
an f/2 lens and 20 ft-c of corrected 
incident light will produce an acceptable 
color picture. 

Figure 29 shows two color cameras in 
operation in CBS Studio 57. The left 
camera takes long shots while the 



camera on the right is used for close-ups. 

Figure 30 is a sketch of the control 
room. In the upper portion are shown 
the color monitors, one each for the live 
cameras, slide projectors, film cameras, 
and one for monitoring the outgoing 
picture. The operator at the extreme 
left controls the audio console; the next 
three operators control the video. Each 
of these also operates a color mixer in 
order to assure optimum color fidelity. 
The remaining indicated personnel are 
the director, the assistant director and 
the technical supervisor. 

Figure 31 is a block diagram of the 
video signal distribution system. Each 
camera has an associated camera con- 
trol, a color mixer and a color monitor. 
Several color monitors are used to permit 
program cuing, timing and overall check- 
ing. 

The outgoing signal is transmitted 
over video lines of the telephone com- 
pany from Studio 57 at 109th Street 
and Fifth Avenue to TV Master Control 
at Grand Central Terminal in New 
York City. From there the signals are 
distributed to network stations and to 
the WCBS-TV television transmitter 
in the Chrysler Building. 5 



IV. Industrial Color Television 



SINCE THE ADVENT of industrial tele- 
vision, its uses have expanded enor- 
mously, and with the addition of color 
there seems to be no limit to the number 
of applications it will satisfy in science, 
medicine, education, industry and 
government. Industrial equipment is 
essentially closed-link equipment de- 
signed with emphasis on rugged ness and 
reliability. Such equipment, designed 
by CBS, is now available and is marketed 
by Remington Rand under the trade 
name "Vericolor." 



*If the infrared sensitivity of image- 
orthicon tubes were sufficiently low, it 
would be possible to dispense with infrared 
filters. 



Figure 32 shows the industrial color 
camera with its control console. Since 
it is desirable to reduce camera weight 
and size to a minimum, the camera 
control equipment, synchronizing signal 
generator, waveform monitoring, etc., 
are all located in the control console. 
The color monitor in the console and 
the optical viewfinder at the camera 
take the place of a color viewer at the 
camera. 



6 W. R. Fraser and G. J. Badgley, "Motion 
picture color photography of color tele- 
vision images," Jour. SMPTE, vol. 54, 
pp. 735-744, June 1950. Motion picture 
color photography of color television 
images has been successfully accomplished 
and is described in the literature. 



Goldmark, Christensen and Reeves: Color Television 



373 




Fig. 34. Monochrome and industrial color television cameras. 




374 



Fig. 35. Industrial color television camera with color-disk drive. 
October 1951 Journal of the SMPTE Vol. 57 




Fig. 36. Industrial color television camera with preamplifier, dynode power 
supply, and image orthicon focus and alignment coils. 



The industrial color camera (exclusive 
of the tripod) weighs only 43 Ib. As 
illustrated in Fig. 33, it is unusually 
compact, being only 23 in. long by 
1\ in. by 1\ in. Figure 34 is a com- 
parison photograph of the RCA mono- 
chrome television camera and the CBS 
industrial color television camera. Fig- 
ures 35 and 36 are interior views of the 
industrial color television camera. 

Camera focusing and lens selection 
are remotely controllable from the 
control console. Any one of three 
lenses in the turret may be selected by 
pressing the corresponding button. Full 
focusing range control is provided for 
the 83-mm and the 135-mm lenses; 
for the 9-in. lens two lens-shifting steps 
of 1-in. each are provided on the 
camera turret in conjunction with a 
remotely controlled continuous travel 
range of \\ in. 

A small synchronous motor operating 
at 1440 rpm drives the 2j-in. diameter 
color filter drum. 

The output voltage of the camera in 
normal use is approximately 0.3 v 
peak-to-peak. This is derived from a 



self-contained preamplifier. The first 
two tubes in this unit function as normal 
wide-band amplifiers with a small 
amount of degeneration in the cathode 
circuits; the output stage is a con- 
ventional triode cathode follower. A 
compact 3-kc, 1500-v supply with its 
voltage divider furnishes all the voltages 
required by the image orthicon tube. 
A 25-ft cable connects the camera to the 
control console. 

This color camera has proved to be 
extremely valuable for live pickup in 
color at low illumination levels. Ac- 
ceptable color images can be obtained 
with only 45 ft-c of incident 3500 K 
fluorescent light and a lens opening of 
//3.5. With incident light of 100 ft-c 
excellent picture quality is obtainable. 

The Control Console 

Figure 37 is a block diagram of the 
complete equipment. The signal leav- 
ing the color camera passes through the 
camera cable to the console (shown in 
Fig. 38) where the following functions 
are performed (the rear of the console 
is shown in Fig. 39): 



Goldmark, Christensen and Reeves: Color Television 



375 




Fig. 37. Industrial color television equipment, block diagram. 



376 



October 1951 Journal of the SMPTE VoL 57 




Fig. 38. Industrial color television monitor console (cover closed). Note The 
oscilloscope in the upper right corner shows red, blue and green signals. 




Fig. 39. Rear view of Fig. 38 showing 3-chassis construction. 
Goldmark, Christensen and Reeves: Color Television 



377 




378 



October 19$ 1 Journal of the SMPTE VoL 57 




Fig. 41. Frequency converter and power supply regulator. 




Fig. 42. Industrial color television monitor. 
Goldmark, Christensen and Reeves: Color Television 



379 



(1) amplification of the video signal; 

(2) reinsertion of the high frequencies 
lost in the camera, the connecting cable, 
and the input circuit of the console; 

(3) electrical separation of the video 
signals representative of the three colors 
in the color mixer so that each may be 
controlled independently as to brightness 
and video level (color mixer); 

(4) recombining the controlled video 
signals; 

(5) amplification and mixing of the 
synchronizing pulses with the video 
signal; 

(6) remote control of camera focus; 

(7) remote control of camera lens 
selection; signal automatically blanked 
during motion of the lens turret; and 

(8) complete color picture monitoring 
of the outgoing signal. 

General Circuits 

Figure 40 is a block diagram showing 
the functions of the color mixer and its 
related circuits. The video amplifier 
consists of five tubes, V5 to V9. It is 
of conventional design with a band- 
width of 10 me. A conventional equal- 
izing circuit is located in the plate load 
of the first stage. Tube VI is used to 
generate a blanking signal which mo- 
mentarily blanks the video amplifier at 
V8 and V9 whenever the turret selection 
button is pressed. Tubes VI 1 to VI 3, 
inclusive, and VI 5 to VI 8, inclusive, 
operate as conventional clampers in 
maintaining the desired black level 
during the blanking signal period. 

Color Mixer 

The signal from V9 is coupled to a 
gamma control amplifier, the output 
of which is branched into three identical 
amplifiers. A gain control is located at 
the input of each of these units. Gating 
is performed by a rectangular wave of 
1/144-second duration at the color re- 
petition rate (48 cycle/sec) which 
originates in the ring circuit to be 
discussed later. In the circuit shown, 
tube VI 1 is the amplifier for red, VI 2 



for blue, and VI 3 for green, each tube 
controlling only one primary color. 
Composite blanking, the amplitude of 
which may be adjusted, is superimposed 
on the plates of these tubes. The output 
is amplified and coupled into a voltage 
divider, which is used as an output gain 
control. Finally, after passing through 
two video amplifier stages, the video 
signal is mixed with the synchronizing 
pulses to form the final output signal. 

Pulse shapes and relative phases from 
the gating ring circuit are shown in 
Fig. 25. 

Sweep Circuits 

The sweep circuits for both the image 
orthicon and the monitor color tube are 
of orthodox design with the exception of 
the special horizontal output trans- 
formers used. 

Audio Equipment 

The audio circuits are mounted on 
the synchronizing signal generator 
chassis. They provide amplified inter- 
communication between the video opera- 
tor, camera man, director, and remote 
locations such as classrooms in other 
buildings. A control tube, V31B, acts 
as a remotely controlled switch, allowing 
extra earphones to be connected across 
the intercommunication circuit. If, for 
instance, a medical student watching an 
operation in a classroom wishes to ask a 
question of the surgeon in the operating 
room, he pushes a button located on the 
intercommunication headset at the color 
receiver. This connects the surgeon's 
hearing-aid-type earpiece across the 
intercommunication circuit. The sur- 
geon answers the question over the 
regular program channel, using a minia- 
ture microphone in his mask. 

The audio circuits in the console also 
provide amplification of the audio 
program. A two-channel microphone 
input and +8VU level balanced output 
are provided. These can accommodate 
the surgeon's microphone and two addi- 
tional microphones. 



380 



October 1951 Journal of the SMPTE Vol. 57 




Fig. 43. Industrial color television monitor chassis. 



Power and Control Circuits 

To effect an overall simplification of 
the equipment, 48-cycle/sec power 
is obtained from a motor-generator set, 
shown in Fig. 41, operable from a 
60-cycle/sec, 3-phase, 4-wire 208-v sup- 
ply. Two hundred eighty volts d-c at 
1 amp is obtained from a conventional 
regulated power supply which is mounted 
with the motor generator on a portable 
assembly. 

A switch on the console remotely 
controls power to the entire equipment. 
Power for field excitation of the motor 
generator is applied approximately 
twenty seconds after the main switch 
has been closed by means of a time-delay 
relay. 

Maintenance and operational checks 
are facilitated by both a meter on the 
regulated supply and test connections 
at the motor generator. 



Color Monitor 

Figure 42 is a photograph of a color 
television industrial monitor showing 
an intercommunication handset recessed 
at the left rear of the console. Figure 43 
shows the chassis construction and 
arrangement of this unit. 

Acknowledgment. This paper in many 
ways is intended as a tribute to that 
handful of tireless and enthusiastic 
workers, namely, the people of the CBS 
Laboratories Division, who helped to 
develop the CBS color television system 
from its modest start in the spring of 
1940 up to the time it became the na- 
tional color television standard after 
gruelling hearings and exhaustive com- 
parative tests. 

To the management of CBS we express 
our appreciation for their never-failing 
faith in our work. Without their 
generous and courageous support this 
new industry would not have been born. 



Goldmark, Christensen and Reeves: Color Television 



381 



A New Technique for Improving the 
Sharpness of Television Pictures 

By PETER C. GOLDMARK and JOHN M. HOLLYWOOD 

In conjunction with the CBS color television system a method has been de- 
veloped for improving the apparent picture definition, called "crispening." 
It uses nonlinear circuitry to decrease the apparent rise time of an isolated 
step input which is applied to a bandwidth limited system. This gives the 
color television pictures (with the exception of repetitive patterns representing 
frequencies beyond system cutoff) the appearance of having been transmitted 
through a system of greater bandwidth. The basic idea is to add to a wave- 
form with a slow transition a second waveform, representing the difference 
between the desired waveform and the original waveform. 

A simple circuit is described which utilizes nonlinear means for reforming 
the roughly triangular differential of the step signal into a narrower "spike" 
roughly triangular in shape which is superimposed on the original waveform 
to obtain a response corresponding to about half the original rise time. 
Various crispening circuits have been designed for specific applications and 
will be discussed in more detail. 



w, 



HEN VIEWING television pictures, 
the observer trying to follow the action 
has little time to delve into any par- 
ticular area .of the picture and focus 
his attention on any one fine detail, 
unless the detail is stationary and of 
some special importance. Nevertheless, 
an observer will always be able to tell 
whether a picture is sharp or fuzzy. 
Experience has shown that pictures 



A contribution submitted September 4, 
1951, by Peter G. Goldmark and John M. 
Hollywood, Laboratories Division, Co- 
lumbia Broadcasting System, Inc., 485 
Madison Ave., New York 22, N.Y. This 
paper is being published simultaneously 
in the Proceedings of the I.R.E. 



appearing sharp do not necessarily con- 
tain extremely small objects, objects so 
small that they require the ultimate 
bandwidth of the system. It is the 
sharpness of objects almost always 
greater than one or two picture elements 
which matters, and the purpose of this 
paper is to report on a method rendering 
outlines of such objects sharper, corre- 
sponding to, roughly, double the band- 
width. 

The overall impression of such a pic- 
ture with sharper outlines can be called 
crisp. The special circuits capable of 
obtaining such an appearance with a 
limited bandwidth, have been called 
crispening circuits. 



382 



October 1951 Journal of the SMPTE Vol.57 



In the CBS field-sequential color 
television system the horizontal resolution 
is a little over half that of standard 
monochrome television. In the tech- 
nique to be described, outlines of objects 
wider than a single picture element can 
be made as sharp as the maximum sharp- 
ness possible in standard monochrome 
pictures as far as the horizontal direction 
is concerned. Naturally, due to the 
4-mc video limitation, the smallest 
object which the color system now can 
depict accurately in a horizontal direc- 
tion is equivalent, roughly, to two mono- 
chrome picture elements. It is seldom, 
however, that the overall sharpness of a 
picture depends on being able to depict 
such small objects accurately. In fact, 
in such cases, by the choice of proper 
lens and camera technique, an object 
when increased a little over 50% in 
linear dimension would have the same 
definition as in the monochrome system. * 

At the outset it should be pointed out 
that crispening has nothing in common 
with peaking, pre-emphasis or aperture- 
correction methods heretofore employed 
for high-frequency pictorial compensa- 
tion, as will be shown in this paper. 

The relation between bandwidth of a 
linear system and rise time for a suddenly 
applied voltage input step is well known. 
This has probably caused the casual 
investigator to dismiss the problem of 
improving rise time as insoluble. How- 
ever, the well-known relations are 
confined to linear systems. Improve- 
ment of the rise time is possible by 
means of nonlinear operations per- 
formed on waveforms associated with a 
system of limited bandwidth. Such 
operations cannot be expected to yield 
a system output if the system input is a 

* The arithmetic mean between the 
number of alternate bright and dark lines 
in the horizontal and vertical directions 
for which total loss of definition occurs is 
a little over 50% greater for monochrome 
than for color. (The ratio of the frame 
frequencies is 2.4:1, so that a ratio of 
linear dimensions of ^/2A or 1.55:1 
would give equal definition.) 



sinusoidal waveform of frequency higher 
than the limited bandwidth will pass. 
No new information can be produced at 
the output, but the original bandwidth- 
limited information can be changed in 
its nature. 

In the case of television pictures, 
high-detail information is, for the most 
part, of the nature of isolated steps, and 
only rarely of a repeated nature ap- 
proximating a steady-state waveform 
made up of frequency components above 
the system bandwidth limit. The 
"crispening" method described ki this 
paper uses nonlinear circuitry to modify 
the nature of the isolated step response 
of bandwidth-limited systems. This gives 
television pictures the appearance of 
having been transmitted through a 
system of greater bandwidth than is 
actually used, except for omission of such 
high-frequency repetitive patterns, and 
inability to resolve closely spaced fine 
lines. 

Basic Approach 

The basic idea is to attempt to add to 
a waveform having a slow transition a 
second waveform which represents the 
difference between the waveform de- 
sired and the waveform originally pres- 
ent. Figure l(a) shows an idealized 
waveform of slow transition, and Fig. 
1 (b) shows a family of curves depicting 
possible waveforms, any one of which 
can be added to it to make the resultant 
have an infinitely fast transition (see 
corresponding curve in Fig. l(c)). As 
a less ambitious illustration, Fig. 2(b) 
shows a family of curves depicting pos- 
sible waveforms which can be added 
to that of Fig. 2 (a) to make the resultant 
have twice the original transition rate 
(Fig. 2(c)). Any of the three wave- 
forms in Fig. 2(c) can be obtained from 
that of Fig. 2 (a) by the use of the corre- 
sponding correction waveform in Fig. 
2(b). It will be noticed that the cor- 
rection waveform of Fig. 2(b) can be of 
a simple shape, for example, either a 
negative or positive triangular spike. 



Goldmark and Hollywood: TV Picture Sharpness 



383 






Fig. 1. (a) Waveform of slow transi- Fig. 2. (a) Waveform of slow transition 

tion rate; (b) added waveform for fast rate; (b) added waveform for twice 

transition rate; (c) resultant waveform transition rate; (c) resultant waveform 

after addition. after addition. 



(A) 




Fc CUTOFF FREQUENCY 
T -TIME 



1.0 




CURVE I- K= 1.8 
" 2.-K--0 
3tK-l.8. 



Fig. 3. (a) Transition waveform of ideal low-pass filter; (b) added 
waveform for twice transition rate. 



384 



October 1951 Journal of the SMPTE Vol.57 



In practice, the type of waveform to 
be corrected would be more like that of 
Fig. 3 (a), the step response of an ideal 
low-pass filter. Any one of the curves 
of Fig. 3(b) represents the correcting 
waveform required to double the transi- 
tion rate. Thus the resultant will 
duplicate the step response of a filter 
of twice the cutoff frequency. The 
correcting waveform could be approxi- 
mated by a negative or positive tri- 
angular spike. 

The negative or positive differential 
of the original waveform can serve as a 
useful approximation. Adding or sub- 
tracting the differential increases the 
transition rate, but may be accompanied 
by "overshoots," which sometimes are 
undesirable. This is to be expected 
since no nonlinear elements are involved. 
Looking at it from the corrective wave- 
form standpoint, the added spike is 
wider than that most desirable. 

If the differential of the original wave- 
form is modified, making it less wide by 
using a nonlinear power law device 
(for example, squaring its amplitude 
for both polarities), a correcting wave- 
form may be obtained, which gives a 
steepened resultant free from overshoot. 
But this holds rigorously for only one 
transition amplitude. If the differential 
of the original waveform is made less 
wide by clipping, passing only the peaks 
of the differential waveform, a correcting 
waveform may be obtained, which also 
gives a steepened resultant free from 
overshoot or undershoot. This result 
also holds true rigorously for only one 
transition amplitude, unless the clipping 
action can be made to follow any change 
in amplitude. 

A shortened spike can be obtained 
from the differential if the latter is made 
available as the voltage from a low- 
impedance source feeding a rectifier 
having a load consisting of resistance and 
capacitance in parallel, and the current 
through the rectifier is used as the output 
spike. The spike amplitude is then 
nearly proportional to the transition 



MAIN SIGNAL PATH 




LOW IMPEDANCE 
SOURCE OF :^T- 
DIFFERENTIATED 
SIGNAL 



^H 

UJ 4 



C- 50 MMFD 
R. 1200 OHM 
R 150 OHM 

SPIKE _ 



OUT 

|Ri 

? DE 
J_ SPIK 



DETAILS OF 
SPIKE PRODUCER 



Fig. 4. Block diagram of simple 
crispening circuit. 

amplitude. This method is employed 
in a practical "crispener" to be described. 
In Appendix A the basic idea will be 
explored further to show that any degree 
of steepness correction in isolated tran- 
sient steps is possible. 

Applications 

Figure 4 is a block diagram of a 
simple crispening circuit based on the 
above method. To insure that a spike 
can be centered halfway up the slope 
of the uncorrected waveform, an ad- 
justable delay is included in the main 
signal path. The frequency response for 
circuits associated with the main signal 
path need only be good enough to ac- 
commodate all frequencies initially pres- 
ent in the input signal. The spike 
path after the spike has been formed, 
and the circuits handling the combined 
output, should preferably have at least 
twice the bandwidth of the input signal. 
Such an arrangement has been used for 
experimental observations and also has 
been tested in conjunction with color 
television receivers. 

In the course of demonstrations of 
color television originating in New York 
studios and being shown in cities as far 
as Chicago, it was desired to apply a 
similar arrangement to the improvement 



Goldmark and Hollywood: TV Picture Sharpness 



385 




386 



October 1951 Journal of the SMPTE VoL 57 



of pictures transmitted by coaxial cable 
for which the cutoff frequency was about 
2.7 me. Several units were built for 
this purpose, of a sufficiently versatile 
nature to warrant giving a detailed 
description. 

Figure 5 is the schematic diagram of 
this special crispener. It handles an 
input of 1.4 v peak-to-peak including 
synchronizing pulses, from a 75-ohm 
line. The output level and polarity 
into a 75-ohm line are the same as for 
the input. The circuits for the main 
signal path and combined output (V l5 
Vfo V a ) are flat within 1 db to 6 me, 
and 3 db down at 9 me. The circuits 
associated with the spike path and 
combined output after spike production 
(Vna, V w , V 13 , V 3 ) are flat within 1 db 
to 8 me, and 3 db down at 10.5 me. 
The main signal path includes a control, 
Ci, to adjust the overall gain to unity, 
and a control, C 2 , to adjust delay in the 
main signal path, to allow shifting 
transitions so that the spike falls on the 
optimum part of the slope. If spikes 
are not injected, the overall output is 
essentially the same as the input except 
for delay. 

Spikes for either direction of transition 
are produced by the crystal rectifiers 
V 9 and VIQ with their associated RC 
loads. The input to the spike-producing 
rectifiers is essentially the differential of 
the input signal, obtained at low im- 
pedance by using a transformer which 
also serves as the differentiating induc- 
tive load for VJB. The spike duration 
is mainly controlled by the RC values in 
series with V 9 and VIQ, although also 
influenced by the frequency responses of 
circuits both preceding and following 
the spike formation. The spike path 
after spike formation includes the tubes 
VuA, Vi2, and Vi 3 ; the plate of the latter 
is in parallel with the plate of V 2 in the 
main signal path, at which point the 
spike is added on to the transition and 
the combined output fed to the output 
cathode follower V 3 . No control is 
provided for spike duration. The RC 



values shown are used for "crispening" 
either coaxial cable television trans- 
missions or transmissions received from 
a standard television transmitter by a 
representative television receiver,